Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Slade on January 11, 2014, 09:36:45 AM
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Hello,
What would you say are the top three planes that retain E (Energy)?
Thanks,
Slade :salute
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Hello,
What would you say are the top three planes that retain E (Energy)?
Thanks,
Slade :salute
I did some testing years ago, and posted it here. The La-7 was the E champ, IIRC.
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Brewster Buffalo :noid.
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Spits are certainly near the top of the list. In level flight if you throttle off they slow down fast but in a combat situation they retain E through a turn like nothing else in the game and while their zoom climb in itself isn't great, their ability to climb combined with WEP compensates nicely.
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P-38 has excellent energy retention, one of its best characteristics.
ack-ack
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I would say the Temp.....LA7....spit 16/8/9
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A-20...but don't tell anyone :noid
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Retaining E is not actually a thing. People use the phrase to refer to both minimizing drag and to slow speed turn performance. Neither retains E and the concept inhibits clear thinking about aircraft performance.
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An aircraft with zero drag would be perfect in retaining energy. In that technical sense, retaining energy thus is the minimization of drag, especially induced drag since it is the larger component during maneuvers with substantial g's. I would think Spitfires would be among the best there. However, during the maneuver, the engine is also contributing energy, so if you include the effect of the engine, it is possible for a plane to go through a maneuver and have more energy at the completion of it back to the same altitude (consider a slight dive starting at 150 mph from 5000 ft to 4000 ft under full power, then back up to 5000 ft and ending up with more than 150 mph). Taking that into account, it could be that an airplane with less induced drag (a Spit I, for example) could be outdone by a plane with a more induced drag but a bigger engine that more than compensates. The La-7 does well there by Widewing's tests.
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Are you ignoring fuel? Fuel is part of the total energy package. You can minimize energy loss but you cannot hold on to it. You are converting some combination of speed, altitude, and fuel.
When people say the Brewster holds E they aren't referring to it's drag. It just has a good slow speed turn. Spits have both low drag and good slow speed turns.
My point is that the popular expression "holds E", is uselessly vague and is misleading. I don't doubt Widewing's results with the La-7, but I don't know what he compared and what he is telling us about it's performance.
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When I tested zoom climbs by 1. Diving to sea level. 2. Waiting for speed to bleed to 400 IAS 3. Doing a 3-G pullup, and 4. Using shift-X to hold the plane straight vertical until it fell off, I found that most ever WWII plane in the game zooms about 6K. But the P-38 held out till 7K in a zoom climb, because the counter-rotating props allow it to hang nose up longer without torque rolling.
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My point is that the popular expression "holds E", is uselessly vague and is misleading.
- When I am in a jug dropping like a brick from 12k, level off on the deck at 500+ mph, then see a Spit16 or N1k 600 out on my 6. I wonder what to call that aspect of the plane that enables that. ...AND what planes do that best.
- When oldcoot SKOOLZ me in his P-51 where we engage with him being just slightly higher than me. He did this by maintaining significantly greater alt and speed leaving me few choices.
In these instance it is not just pilot ACM skills (though oldcoot certainly has them). The pilots in these and similar cases are taking advantage of __________ (insert preferred technical term). I simply want to learn what IT is and get good at using IT. I think we all would, who have not already mastered it.
Thanks all for your posts and advice.
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Are you ignoring fuel? Fuel is part of the total energy package. You can minimize energy loss but you cannot hold on to it. You are converting some combination of speed, altitude, and fuel.
When people say the Brewster holds E they aren't referring to it's drag. It just has a good slow speed turn. Spits have both low drag and good slow speed turns.
My point is that the popular expression "holds E", is uselessly vague and is misleading. I don't doubt Widewing's results with the La-7, but I don't know what he compared and what he is telling us about it's performance.
Well, the term E doesn't refer to the next hour. It refers to how much E the aircraft has to use at a given moment. A P-51 cannot take 100 gallons of fuel and burn it in a few seconds to gain E on a Spitfire that cannot match that fuel burn rate. The P-51B and Spitfire Mk IX in AH will actually burn fuel at almost exactly the same rate so how much E they will have in 45 minutes (none for the Spit as it'll have run out of fuel 15 minutes earlier) is useless data in terms of the E they have as they engage each other.
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Yeah, E retention isn't defined enough. But only a few factors need to be taken into consideration. Horsepower, weight, and drag. (Horsepower/lb weight)/(total drag).
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Hello,
. . .top three planes that retain
F4U1A
Brewster
Ki
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...
Brewster
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No. Brewster is absolutely terrible at holding its E.
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There are several kind of "holding E":
Speed bleed at higher than max level speed
This refers to diving into a speed the plane cannot sustain and waiting for the speed (kinetic energy) to sip away. Specific drag (drag/mass ratio) is very important here. Also engine power and some properties of the prop help because at high speeds the prop produces drag.
Speed bleed while maneuvering
This refers to energy bleed while pulling G. In addition to form-drag, induced drag play a large role. Induced drag roughly behaves like the lift squared (D~L^2) and if we are maintaining a constant G, that means also D~G^2. The exact proportionality depends on the wing-loading (because less weight means less lift is required to maintain G) and the properties of the wing. A spitfire has large wings for its mass that provide quite low mass loading and they are elliptical, a shape that reduce the induced drag. This is why Spits keep their speed up "well" even in a high G turn. I have seen Yak3s with a dead engine keep fighting, scissoring, circling a base and landing with what seemed like minimal energy loss while maneuvering. Not sure why, but I did not check its wing loading numbers. Most other planes would have fallen out of the sky if they tried that.
Now, planes do not have to hold their E - they can spend it and immediately replenish it by engine power. Therefore, high power loading can replace aerodynamic efficiency in "keeping E" and the engine helps in sustaining hard turns. La7s and 109K4s immediately come to mind as examples. There are planes that combine several qualities - Spit16s and Yak3s have a good power loading and seem to suffer very little from drag at high G.
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- When I am in a jug dropping like a brick from 12k, level off on the deck at 500+ mph, then see a Spit16 or N1k 600 out on my 6. I wonder what to call that aspect of the plane that enables that. ...AND what planes do that best.
- When oldcoot SKOOLZ me in his P-51 where we engage with him being just slightly higher than me. He did this by maintaining significantly greater alt and speed leaving me few choices.
In these instance it is not just pilot ACM skills (though oldcoot certainly has them). The pilots in these and similar cases are taking advantage of __________ (insert preferred technical term). I simply want to learn what IT is and get good at using IT. I think we all would, who have not already mastered it.
Thanks all for your posts and advice.
Specific questions like those are more useful. You can get your best answers when you have film.
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Bozon you're using energy bleed to illustrate energy retention.
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Unlike diving, weight affects zoom climbing because zoom climbing is all about momentum and inertia. That's why the b239, which is less than half as heavy as an f6f, is a crappy zoomer. Sometimes people confuse zoom climb with "hanging on the prop" like in a roping stallfight or something.
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Unlike diving, weight affects zoom climbing because zoom climbing is all about momentum and inertia. That's why the b239, which is less than half as heavy as an f6f, is a crappy zoomer.
That is not correct. You zoom against drag from air resistance and gravity, but in a climb it's mostly gravity and the drag from gravity is proportional to mass.
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Inertia is proportional to an objects mass, gravity affects all objects equally regardless of mass. Gravitation is proportional to mass, but that has nothing to do with airplanes.
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Inertia is proportional to an objects mass, gravity affects all objects equally regardless of mass. Gravitation is proportional to mass, but that has nothing to do with airplanes.
Then why does a heavier aircraft require more lift?
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The same reason an aircraft carrier requires more thrust than a jet ski. Or more to the point with regards to E retention, the same reason an aircraft carrier requires more force to decelerate than a jet ski requires. Inertia.
Also a zoom climb isn't a product of lift it's a product of ballistic, or kinetic energy. In fact another term for zoom climb is ballistic climb, it's a climb in which an aircraft exceeds it's climb rate by expending it's momentum upward. Just like any ballistic object, the heavier it is, the more it takes to stop it.
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Are you ignoring fuel? Fuel is part of the total energy package.
So you're saying a glider doesn't have E? I disagree. Speed (kinetic energy) an altitude (potential energy) are the only components of E. Show me a reputable source that adds fuel to that equation.
Thrust, lift and drag act on E. The only effect fuel has is allowing an engine to run thus producing thrust but fuel in and of itself has nothing to do with E.
And you can retain E. As long as you hold the same overall balance of speed and altitude you've retianed E. Gliders do it all the time. If all they did was lose E they wouldn't fly very long but, in fact, they can stay aloft for very long times and again, they do so without fuel.
And yes, heavier aircraft typically, but not always, zoom climb better than lighter ones. It's because the E reducing forces have to work against a much larger mass. Think of it this way; if you had a bicycle and a train both rolling toward you at the same speed without power which would you have a harder time stopping?
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The same reason an aircraft carrier requires more thrust than a jet ski. Or more to the point with regards to E retention, the same reason an aircraft carrier requires more force to decelerate than a jet ski requires. Inertia.
Also a zoom climb isn't a product of lift it's a product of ballistic, or kinetic energy. In fact another term for zoom climb is ballistic climb, it's a climb in which an aircraft exceeds it's climb rate by expending it's momentum upward. Just like any ballistic object, the heavier it is, the more it takes to stop it.
It's gravity that gives it weight and it's gravity that slows it down until it stops climbing.
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So you're saying a glider doesn't have E? I disagree. Speed (kinetic energy) an altitude (potential energy) are the only components of E. Show me a reputable source that adds fuel to that equation.
Thrust, lift and drag act on E. The only effect fuel has is allowing an engine to run thus producing thrust but fuel in and of itself has nothing to do with E.
And you can retain E. As long as you hold the same overall balance of speed and altitude you've retianed E. Gliders do it all the time. If all they did was lose E they wouldn't fly very long but, in fact, they can stay aloft for very long times and again, they do so without fuel.
Sailplanes require thrust to fly. I'm aware of the lack of engine, excepting motor gliders of course. The fact that their trust comes from gravity doesn't change the fact that all aircraft convert energy in order to fly.
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That is not correct. You zoom against drag from air resistance and gravity, but in a climb it's mostly gravity and the drag from gravity is proportional to mass.
Im not busting your chops. But it is important to me that you understand that drag from gravity is not proportional to mass. If one dropped a BB and a cannon ball at the same time from the tower of Pisa, the BB and the cannon ball would both hit the ground at the same time.
Or if you dropped a feather and a hammer at the same time in a vacuum..
http://youtu.be/5C5_dOEyAfk
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Bozon you're using energy bleed to illustrate energy retention.
Because they refer to the same thing. Less energy bleed is the same as more energy retention. For me it is more convenient to think in terms of what makes me lose energy, rather than how much energy I get to keep.
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Im not busting your chops. But it is important to me that you understand that drag from gravity is not proportional to mass. If one dropped a BB and a cannon ball at the same time from the tower of Pisa, the BB and the cannon ball would both hit the ground at the same time.
Or if you dropped a feather and a hammer at the same time in a vacuum..
http://youtu.be/5C5_dOEyAfk
You seem to be saying that gravity doesn't affect things equally going up, just going down. I'm saying it's the same in both directions.
It's because gravity is proportional that the hammer and feather fall together in a vacuum. Greater mass has greater inertia and requires greater force to accelerate. Works both ways.
Because they refer to the same thing. Less energy bleed is the same as more energy retention. For me it is more convenient to think in terms of what makes me lose energy, rather than how much energy I get to keep.
I'm not disagreeing with you. My point is that referring to energy is not the best way to talk about speed and altitude. I understand that people generally refer to energy as being the speed and altitude of an aircraft and that it's a simplified explanation of energy. I agree it's important for people to understand how we trade kinetic and potential energy and how we combine them to compare relative energy states. However the word energy is often used when the words speed or altitude would be clearer and easier for less expert readers to understand.
Saying that turning hard bleeds E is not as descriptive as saying that turning hard slows you down. It's confusing for the guys trying to learn ACM and leads to nonsense like "spits hold E better in turns". Every aircraft slows down when you increase drag. Every aircraft retains all it's speed and altitude when you maintain level flight and don't increase drag. What Spits do, as you know, is allow a higher load factor at slow speeds than many other of our fighter aircraft. Describing that as holding E better isn't a useful description. Saying that they have lower stall speeds and/or better sustained turns is simpler and easier to quantify.
The OP had at least 4 good questions rolled into his first one but thinking in terms of the best energy retaining aircraft wasn't helping him.
Fortunately training is available. :D
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The two important factors in a zoom climb are power/weight and thrust/weight. I know this because Mace said so :-) Plus eventually the ability to hold the thing steady as the speed bleeds off.
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If one dropped a BB and a cannon ball at the same time from the tower of Pisa, the BB and the cannon ball would both hit the ground at the same time.
Not true, they would hit the ground at different times and the difference would be due to their mass.
If you write the equation of motion for the BB and the cannon ball you start with Newton's law:
f = m a
The force f downwards is gravity and is equal to mg and the force upwards caused by air resistance is -d giving
mg-d = ma
then divide both sides by m gives
a = g - d/m
This means that for the same drag the heavier object will have greater acceleration to the ground.
In a zoom climb similar reasoning applies, so starting with Newton's law again:
f = ma
this time the gravity and drag both act in the same direction, so we have:
-mg-d = ma
dividing both sides by mass gives
-a = g + d/m
This shows that ballistically the heavier object will have smaller deceleration and thus zoom higher.
The situation is more complicated when thrust is included, but leaving thrust out does help clarify the effect of mass and gravity.
Regards
Badboy
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This shows that ballistically the heavier object will have smaller deceleration and thus zoom higher.
The situation is more complicated when thrust is included, but leaving thrust out does help clarify the effect of mass and gravity.
Regards
Badboy
The problem is that many people expect more exaggerated differences than they get. A P-47 initiating a zoom climb from 300mph will end up higher than an A6M doing the same, but not all that much higher. People often seem to expect the P-47 would double, or better, the A6Ms zoom climb.
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The problem is that many people expect more exaggerated differences than they get. A P-47 initiating a zoom climb from 300mph will end up higher than an A6M doing the same, but not all that much higher. People often seem to expect the P-47 would double, or better, the A6Ms zoom climb.
Weight/drag ratio (ballistic) is a factor, but I think it was Mace again who explained on a thread that in airplane zoom performance it is a minor factor compared to thrust/weight and thrust/drag ratio.
In my tests, from going on the deck 400, you can expect to get back 6000 some odd feet. Held true with every plane tested. The best was the P-38, which got 7K purely because its can point it's nose at the sky longer because of no net torque.
IIRC, the section on energy fighting in "Fighter Combat" by Shaw suggests having at least a 100mph speed advantage to safely deny the lower energy bandit the ability to zoom with you.
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It's because gravity is proportional that the hammer and feather fall together in a vacuum.
Please explain.
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Not true, they would hit the ground at different times and the difference would be due to their mass.
If you write the equation of motion for the BB and the cannon ball you start with Newton's law:
f = m a
The force f downwards is gravity and is equal to mg and the force upwards caused by air resistance is -d giving
mg-d = ma
then divide both sides by m gives
a = g - d/m
This means that for the same drag the heavier object will have greater acceleration to the ground.
In a zoom climb similar reasoning applies, so starting with Newton's law again:
f = ma
this time the gravity and drag both act in the same direction, so we have:
-mg-d = ma
dividing both sides by mass gives
-a = g + d/m
This shows that ballistically the heavier object will have smaller deceleration and thus zoom higher.
The situation is more complicated when thrust is included, but leaving thrust out does help clarify the effect of mass and gravity.
Regards
Badboy
Yes because of air resistance the BB falls slower but I was referencing galileos experiment to show that the effects of gravity on an object aren't proportional to the objects mass.
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Yes because of air resistance the BB falls slower but I was referencing Galileo experiment to show that the effects of gravity on an object aren't proportional to the objects mass.
That only works if the bbs and cannon are starting at the smae place at at the same time. Take a .243 55grain shell. It has a muzzle velocity of 3500fps where as a 50 bmg has a muzzle velocity of around 2100-2300 fps. The fact that the 50 around 800 grains is the determing factor that it will go farther in the verticle.
Same thing as throwing a tennis ball versus a baseball. The baseball will go farther due to the fact of more mass.
Galileo's expermint was dropping the objects from the same height. That is the determing factor.
As to the fact that you need 100mph over adversary is how well and how long he can hang on his prop. As it has been pointed out already. Even if you have 100mph advantage over the P-38 he is still going to hang under you longer and will be able to get a lucky shot off in the least.
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Please explain.
The force of Gravity is a constant multiplied by the mass of an object. The greater the mass the more force.
Badboy if we consider air resistance don't we have to consider the different coefficients of drag in different aircraft too?
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P-38 has excellent energy retention,
Especially when I am trying to slow down to land. :airplane:
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Not true, they would hit the ground at different times and the difference would be due to their mass.
Nope, they would hit at different times, but not because of their mass, because of the difference in air resistance. Acceleration due to gravity is 32ft per second, regardless of mass. But greater air resistance will cause one to fall slower.
If you take to objects, with differing mass, but equal air resistance, they will both fall at the same speed. If you have a 500 pound weight, and a 50 pound weight, and both have the same air resistance, and you drop both from the same height at the same time, they will both hit the ground at the same time. Acceleration due to gravity is the same for both. Drag due to air resistance is what would make one fall faster.
Now, let's say these two weights are airplanes with identical aerodynamic characteristics. The 500 pound airplane and the 50 pound airplane both dive straight towards the ground. As long as they have identical drag, they both dive side by side at the same speed. Now they pull out of the dive (not crashing into the ground, like I normally do :bhead). The 500 pound airplane will have much more energy, because of its greater weight. Cut the throttles, and go into a climb, and the 500 pound airplane will go much higher, because it's greater weight gives it more energy to use in the fight against gravity.
Now, in level flight, or even a turn fight, the lighter plane can have the advantage because it's engine can push it faster.
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Nope, they would hit at different times, but not because of their mass, because of the difference in air resistance. Acceleration due to gravity is 32ft per second per second, regardless of mass. But greater air resistance will cause one to fall slower.
Fixed
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The force of Gravity is a constant multiplied by the mass of an object. The greater the mass the more force.
The greater the mass the more inertial force. The feather fell as fast as the hammer because gravity exerted equal force on the hammer and the feather, thus the force of gravity can not be increased or decreased by an objects mass. That means the force of gravity is not proportional to the objects mass.
Mongoose is right.
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The greater the mass the more inertial force. The feather fell as fast as the hammer because gravity exerted equal force on the hammer and the feather, thus the force of gravity can not be increased or decreased by an objects mass. That means the force of gravity is not proportional to the objects mass.
Mongoose is right.
The force per unit of mass is constant. As Badboy put it, f = ma. For every unit of mass the force is increased. The force is in proportion to the mass.
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So this is a thread about the best energy fighters...
I'd consider these being the top 5
109K4
F4U4
190D
P51
P47M
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The force per unit of mass is constant. As Badboy put it, f = ma. For every unit of mass the force is increased. The force is in proportion to the mass.
As you see in F=ma, gravity isn't part of the equation. F=ma, even in a zero gravity enviornment. The force you speak of being calculated with that formula is inertia. Galileo was right.
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As you see in F=ma, gravity isn't part of the equation. F=ma, even in a zero gravity enviornment. The force you speak of being calculated with that formula is inertia. Galileo was right.
The a is acceleration and refers to gravity.
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Nope, they would hit at different times, but not because of their mass, because of the difference in air resistance. Acceleration due to gravity is 32ft per second, regardless of mass. But greater air resistance will cause one to fall slower.
Nope, with the same air resistance the one with the greater mass will fall more quickly. If you take two identical hollow balls and fill one with lead and the other with water so that the drag is the same for both, the ball filled with lead will accelerate more quickly as indicated by the equation derived earlier:
a = g - d/m
What happens is that as the mass gets bigger the -d/m term gets smaller thus allowing the ball to fall closer to the acceleration due to gravity and thus faster than a lighter object. As the mass gets smaller the -d/m term gets bigger reducing the acceleration, until eventually if the mass gets low enough the object would float down very slowly.
For objects with the same air resistance the accelerations will be different and the reason is due to their different mass, not different air resistance.
If you take to objects, with differing mass, but equal air resistance, they will both fall at the same speed.
Nope, the heavier object will fall more quickly as indicated by the equation of motion derived earlier.
Regards
Badboy
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Badboy if we consider air resistance don't we have to consider the different coefficients of drag in different aircraft too?
That depends what you are trying to do. If you want to compare how two different aircraft will behave in a dive or a zoom then you need to consider everything.
However, if you are only trying to see how one particular thing will influence the performance, it helps to hold everyhing else constant if possible to get a true comparison. So to see how weight influences a zoom climb it might be helpful to consider two identical aircraft that differ only in weight.
Regards
Badboy
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Top E planes are in two categories. You have aircraft that accelerate the best have either very big engines (like a LA-7) and those with the low drag coefficient ratios and a mid-power engine (like a P-51 Mustang). We have two completely different things happeneing in both aircraft categories.
POWER: In a vertical climb as drag becomes less of a factor as the airspeed drops, the aircraft's ability to pull itself forward (thrust) will help maintain a climb the best. Pure physics. It's why the La-7 and the Bf-109K-4 are climbing beasts.
LOW DRAG: In a vertical climb, as the P-51 and Spitfire climb, their low drag coefficients help reduce wasted energy in a climb with their moderately powerful engines assisting in the climb.
In practical terms, you could do the test two ways. One with the engine 100% with WEP on at 250MPH then point straight up . The second with aircraft at 250MPH then turn engines off and begin the climb. The results will be completely different than the ones with engines on.
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As you see in F=ma, gravity isn't part of the equation. F=ma, even in a zero gravity enviornment. The force you speak of being calculated with that formula is inertia. Galileo was right.
It can be useful to demonstrate this by writing the equation of motion without the drag term so you get:
f = ma
In this case the only force is gravity which is equal to mg so the equation becomes
mg = ma
The mass term cancels from both sides of the equation giving:
a = g
Which in effect tells us that if gravity is the only force, then the acceleration will always be the same and equal to g. However the problem with that statement, is that the only force is not gravity, there are aerodynamic forces involved which can not be ignored when you are talking about aircraft. Talking about a ball falling in a vacuum may make some sense in that context, but it makes no sense when talking about aircraft because you need an atmosphere to provide the forces that make flight possible. You can't then ignore air resistance no matter how convenient it might be.
The simple fact is that the only equations that make any sense include the drag term, and when you include the drag term the acceleration will be different when the mass is different as given by these two equations depending on if the object is going down or up
a = g - d/m
-a = g + d/m
These equations tell us that as long as the object is moving in air, which for aircraft they always will be, then the acceleration will depend on the mass.
They math and physics doesn't get much simpler than that.
Regards
Badboy
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It can be useful to demonstrate this by writing the equation of motion without the drag term so you get:
f = ma
In this case the only force is gravity which is equal to mg so the equation becomes
mg = ma
The mass term cancels from both sides of the equation giving:
a = g
Which in effect tells us that if gravity is the only force, then the acceleration will always be the same and equal to g. However the problem with that statement, is that the only force is not gravity, there are aerodynamic forces involved which can not be ignored when you are talking about aircraft. Talking about a ball falling in a vacuum may make some sense in that context, but it makes no sense when talking about aircraft because you need an atmosphere to provide the forces that make flight possible. You can't then ignore air resistance no matter how convenient it might be.
The simple fact is that the only equations that make any sense include the drag term, and when you include the drag term the acceleration will be different when the mass is different as given by these two equations depending on if the object is going down or up
a = g - d/m
-a = g + d/m
These equations tell us that as long as the object is moving in air, which for aircraft they always will be, then the acceleration will depend on the mass.
They math and physics doesn't get much simpler than that.
Regards
Badboy
Unless we also factor in drag coefficient, these figures mean absolutely nothing. As aircraft speed is measured in HUNDREDS of miles an hour, it has a significant impact on it's ability to maintain E and top speed.
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Unless we also factor in drag coefficient, these figures mean absolutely nothing.
Don't forget thrust as well.
For aircraft the situation is complicated and without a complete model all you can do is generalize about how certain things influence the whole.
Fortunately we are lucky to have a complete flight model provided by HTC, so we can all be flight test engineers :)
Regards
Badboy
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Exactly, air resistance affects how fast an object falls. Heavier objects need bigger parachutes because heavier objects have more inertia. Not because gravity makes heavier objects fall faster, but because heavier objects have more inertia and require more resistance to be slowed.
Mass has no affect on the acceleration of falling objects. Gravity accelerates all objects at the same rate regardless of mass. Embrace it. It's the law.
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Exactly, air resistance affects how fast an object falls. Heavier objects need bigger parachutes because heavier objects have more inertia. Not because gravity makes heavier objects fall faster, but because heavier objects have more inertia and require more resistance to be slowed.
Mass has no affect on the acceleration of falling objects. Embrace it. It's the law.
I think you're confusing the rate of acceleration with the amount of force required to achieve that rate.
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I am sure that I am not.
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The Gravitational attraction of Chuck Norris keeps the Earth and everything on it from floating away.
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Exactly, air resistance affects how fast an object falls.
Not just air resistance, the acceleration is also influenced by the mass as you can see in this equation of motion:
a = g - d/m
Here two objects with the same drag will accelerate differently depending on their mass.
Mass has no affect on the acceleration of falling objects.
No, that is only true when the object is falling in a vacuum, which is not a very helpful assumption when discussing aircraft because they need the atmosphere to fly. Once you accept your object is falling through the atmosphere your statement no longer holds and the acceleration is influenced by the mass of the object as explained.
Gravity accelerates all objects at the same rate regardless of mass. Embrace it. It's the law.
You need to relax that embrace and let it go, because you don't find many objects falling in vacuums. The only law you need here is Newton's law with all the force terms included, because you can't leave out air resistance and get meaningful results.
Regards
Badboy
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Nope, with the same air resistance the one with the greater mass will fall more quickly.
Nope. Wrong. With the same air resistance both objects will fall at the same rate, regardless of their mass. Galileo supposedly did an experiment by dropping two balls of differing weights from the top of the leaning tower of Pisa, and both balls hit at the same time.
The Apollo astronauts confirmed it on the moon. One of the astronauts dropped a feather and a hammer at the same time, and they hit the surface at the same time.
So, if you take wind resistance out of the equation, two objects of differing masses will fall at the same speed. So if you have two objects with same air resistance, they will fall at the same speed, even if one is much heavier than the other. The mass will not affect the dive rate, only the aerodynamic drag will.
However, when you pull out of the dive, the object with more mass will have more momentum, and will go higher in a zoom climb.
This is the way the world works. It has been tested, and proven.
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Nope. Wrong. With the same air resistance both objects will fall at the same rate, regardless of their mass.
No, that's not the way it works and I'm going to try to explain it differently for you, and confirm it with an experiment of my own.
The Apollo astronauts confirmed it on the moon. One of the astronauts dropped a feather and a hammer at the same time, and they hit the surface at the same time.
Ok, that part is correct and to confirm that we can use Newton's second law like this:
Newton's second law is f = ma
On the moon the only force is gravity and the force due to gravity is given by mg so the equation becomes:
mg = ma
Now you see that the mass cancels out on both sides leaving g = a
which means that the acceleration equals gravity and the mass makes no difference. That is what you are saying, and I agree that on the moon or in a vacuum that is true. However, you then extend that to motion in the atmosphere and you simply can't do that. When you take into account the additional forces, the acceleration then depends on mass as well.
So, if you take wind resistance out of the equation, two objects of differing masses will fall at the same speed.
Yes, that's exactly what happens on the moon, no atmosphere, no resistance, no difference in speed and we just used Newton's second law to confirm that.
So if you have two objects with same air resistance, they will fall at the same speed, even if one is much heavier than the other.
No, you can't extend your argument about what happens on the moon to what happens in atmospheric flight, that's a non sequitur. I will shortly prove that mathematically and confirm it experimentally.
The mass will not affect the dive rate, only the aerodynamic drag will.
Again, this is incorrect, both the drag and the mass affect the acceleration. In order to prove that first we can use Newton's second law to demonstrate the truth of it mathematically and then carry out an experiment to confirm it. The experiment was fun, I took some time between teaching today and a couple of my students volunteered to do the experiment so I could show it to you. It isn't as dramatic as dropping cannon balls from a tower, but the results are just as impressive.
Ok, firstly the math and again we will begin with Newton's second law, f=ma. However now the force is not just the force of gravity, there is also the air resistance which is represented with the letter d, so the force is now the gravity acting downwards and the resistance acting upwards so we have f = mg-d and Newtons law can now be written as:
ma = mg - d
now if we divide both sides by m we get:
a = g - d/m
You can read this as the acceleration equals gravity minus the drag divided by the mass. This makes it clear that the acceleration has an upper limit of g, and how much acceleration depends on the value of three things, g, d and m. You can also see that if you apply this equation to two objects that are identical in every way accept their mass, the heavier one will fall faster because d/m will be smaller, and it will reach a higher terminal velocity.
Now for the experiment.
After I read your message I devised an experiment to confirm the theory that was quick and easy to carry out.
Firstly I took two identical table tennis balls, and used a syringe to fill one with water.
(http://www.leonbadboysmith.com/images/Experiment2.jpg)
These two balls then had identical drag, the only difference being that one had greater mass.
According to you, they should both accelerate at the same rate and hit the ground together. According to Newton's second law the heavier one should accelerate faster and hit the ground first.
This is what happened when one of my students dropped the two table tennis balls at the same time, the ball filled with air is in his left hand and the one filled with water is in his right hand.
www.leonbadboysmith.com/video/Experiment.MOV
If you use the pause button to watch what happens you will see that the lighter ball in the left hand appears to be released a fraction of a second before the other and when it passes the dropper's chin it is slightly in the lead, but the heavier ball quickly overtakes the lighter ball and hits the ground with a lead of about four ball diameters. This experiment confirms the theory. In an atmosphere, mass does affect how fast things fall.
This is the way the world works.
Fortunately, it actually works in accordance with Newton's laws, if not those Apollo astronauts would never have made it to the moon in the first place.
Hope this helps...
Badboy
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Nope. Wrong. With the same air resistance both objects will fall at the same rate, regardless of their mass. Galileo supposedly did an experiment by dropping two balls of differing weights from the top of the leaning tower of Pisa, and both balls hit at the same time.
That's because, for those spheres, D/m is small at the speeds experienced in a drop from the tower. As pointed out, a = g - D/m. When D/m is small compared to g, the equation of motion is approximately independent of m.
However, if d/m is not small compared to g, it matters. Drop a feather and a bowling ball from the Tower of Pisa, and the bowling ball will hit the ground first. That's because for the bowling ball g >> D/m and for the feather is about the same size as g. This is an extreme example, but I'll give another one below.
The Apollo astronauts confirmed it on the moon. One of the astronauts dropped a feather and a hammer at the same time, and they hit the surface at the same time.
That's because there is no air on the moon and thus no d. In this case ma = mg, thus a = g, and the equation of motion is independent of mass.
---- Case with More Detail ----
In more detail, D = 0.5 * rho * v^2 * A * C_D, where rho is air density, v is object velocity through the air, A is frontal area, and C_D is coefficient of drag.
Let's take the example of two sphere-like objects of exactly the same size but radically different masses: an air balloon (filled with air, not helium, so we are not talking about buoyancy here) and the same balloon of the same size filled with water. Intuitively, you know that dropping them from the Tower of Pisa, the air balloon will drift down slowly and that the water balloon will plummet down and hit first. In terms of math, it is only because, for the water balloon, g >> D/m, but not for the air balloon.
Let's see what these numbers really are. g = 9.8 m/s^2. Let's take a balloon that is 10" diameter (like these http://www.amazon.com/Shipping-Free--germany-Advertising-Natural-Balloons/dp/B00809SWMQ/ref=sr_1_4?s=toys-and-games&srs=3017937011&ie=UTF8&qid=1389916292&sr=1-4&keywords=balloons (http://www.amazon.com/Shipping-Free--germany-Advertising-Natural-Balloons/dp/B00809SWMQ/ref=sr_1_4?s=toys-and-games&srs=3017937011&ie=UTF8&qid=1389916292&sr=1-4&keywords=balloons) ), so A = pi * (10 * 2.54 / 100 / 2)^2 = pi * 0.13^2 = 0.05 m^2. The package of 100 of these is 0.36 kg, so each balloon weighs 0.0036 kg at most. rho at sea level is 1.2 kg/m^3. For a sphere, C_D is about 0.5. Volume of the balloon is about 4/3 * pi * r^3 = 4/3 * 3.1415 * 0.13^3 = 0.0092 m^3. Water density is 1000 kg/m^3, so that volume of water has a mass of 9.2 kg.
Thus, for the air balloon, D/m = 0.5 * rho * A * C_D / m * v^2 = 0.5 * 1.2 * 0.05 * 0.5 / 0.0036 * v^2 = 4.2 * v^2.
For the water balloon, D/m = 0.5 * 1.2 * 0.05 * 0.5 / (0.0036 + 9.2) * v^2 = 0.0016 * v^2.
D/m for the air-filled balloon is 2600 times higher than D/m for the water balloon. At D/m of the air balloon is equal to g (i.e. terminal velocity) already at only 1.5 m/s. It will accelerate to 1.5 m/s then drift down the rest of the way at 1.5 m/s.
For the water balloon, at 1.5 m/s, D/m is 0.0036 m/s^2 -- negligible compared to 9.8 m/s^2. Terminal velocity of the water balloon is 78 m/s. So, for the water balloon, D/m is insignificant in a drop test (except for very long drops, where v can get up near 78 m/s for a significant portion of the test).
This is all assuming I haven't made any math errors, of course.
Drop these two on the moon (where rho is almost zero), and they will drop the same. Drop them in our sea level atmosphere, and you will get very different behavior.
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Heh! While I was typing some math, Badboy posted an actual experiment. :aok
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No, that's not the way it works and I'm going to try to explain it differently for you, and confirm it with an experiment of my own.
Ok, that part is correct and to confirm that we can use Newton's second law like this:
Newton's second law is f = ma
On the moon the only force is gravity and the force due to gravity is given by mg so the equation becomes:
mg = ma
Now you see that the mass cancels out on both sides leaving g = a
which means that the acceleration equals gravity and the mass makes no difference. That is what you are saying, and I agree that on the moon or in a vacuum that is true. However, you then extend that to motion in the atmosphere and you simply can't do that. When you take into account the additional forces, the acceleration then depends on mass as well.
Yes, that's exactly what happens on the moon, no atmosphere, no resistance, no difference in speed and we just used Newton's second law to confirm that.
No, you can't extend your argument about what happens on the moon to what happens in atmospheric flight, that's a non sequitur. I will shortly prove that mathematically and confirm it experimentally.
Again, this is incorrect, both the drag and the mass affect the acceleration. In order to prove that first we can use Newton's second law to demonstrate the truth of it mathematically and then carry out an experiment to confirm it. The experiment was fun, I took some time between teaching today and a couple of my students volunteered to do the experiment so I could show it to you. It isn't as dramatic as dropping cannon balls from a tower, but the results are just as impressive.
Ok, firstly the math and again we will begin with Newton's second law, f=ma. However now the force is not just the force of gravity, there is also the air resistance which is represented with the letter d, so the force is now the gravity acting downwards and the resistance acting upwards so we have f = mg-d and Newtons law can now be written as:
ma = mg - d
now if we divide both sides by m we get:
a = g - d/m
You can read this as the acceleration equals gravity minus the drag divided by the mass. This makes it clear that the acceleration has an upper limit of g, and how much acceleration depends on the value of three things, g, d and m. You can also see that if you apply this equation to two objects that are identical in every way accept their mass, the heavier one will fall faster because d/m will be smaller, and it will reach a higher terminal velocity.
Now for the experiment.
After I read your message I devised an experiment to confirm the theory that was quick and easy to carry out.
Firstly I took two identical table tennis balls, and used a syringe to fill one with water.
(http://www.leonbadboysmith.com/images/Experiment2.jpg)
These two balls then had identical drag, the only difference being that one had greater mass.
According to you, they should both accelerate at the same rate and hit the ground together. According to Newton's second law the heavier one should accelerate faster and hit the ground first.
This is what happened when one of my students dropped the two table tennis balls at the same time, the ball filled with air is in his left hand and the one filled with water is in his right hand.
www.leonbadboysmith.com/video/Experiment.MOV
If you use the pause button to watch what happens you will see that the lighter ball in the left hand appears to be released a fraction of a second before the other and when it passes the dropper's chin it is slightly in the lead, but the heavier ball quickly overtakes the lighter ball and hits the ground with a lead of about four ball diameters. This experiment confirms the theory. In an atmosphere, mass does affect how fast things fall.
Fortunately, it actually works in accordance with Newton's laws, if not those Apollo astronauts would never have made it to the moon in the first place.
Hope this helps...
Badboy
That's because the heavier ball has more inertia. Inertia is proportional to mass, gravity isn't. Scroll up and see what I wrote about parachutes.
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Drop these two on the moon (where rho is almost zero), and they will drop the same. Drop them in our sea level atmosphere, and you will get very different behavior.
But not because gravity acts on things differently on earth than it does on the moon or a vacuum.
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But not because gravity acts on things differently on earth than it does on the moon or a vacuum.
Of course not. I don't think that I implied that. (However, if you want to get picky in terms on non-Newtonian physics, there is some uncertainty about 90% or more of the mass-energy in the universe, the possibility that the cosmological constant is more than just a fudge factor, and so forth, and how some fundamental things, which we previously thought were constants, might vary in space or time or both. But that, too, was not part of or implied in my discussion. ;) )
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Power/weight ratio, power/drag ratio and weight/drag ratio. Those are the only things that matter in a zoom climb after the rotation into a climb has been made. Wing loading plays a part in how much drag is generated during the rotation into climb. Gravity affects all objects equally (no matter on Earth or the Moon) and is irrelevant.
High power to weight.
High power to drag.
High weight to drag (or more intuitively low drag to weight).
The aircraft with the best overall of those stats will zoom climb the best.
The reason a one pound steel ball falls faster than a ten pound cotton ball is because it has a higher weight to drag ratio, noting more. Eliminate aerodynamic drag (as if on the Moon) and they both accelerate and fall equally fast regardless of weight/mass. Typically the bigger the plane the better weight to drag ratio it has. That's why bigger ships and aircraft are usually more efficient and economical than smaller ones.
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So do we all agree that gravity is not proportional to mass?
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What do you mean by "proportional" ?
Gravity on Earth is a constant 1G acceleration towards the ground, regardless of size or mass.
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Scroll back to see how this thread jumped the tracks.
Is there a formula that can express how fast I don't care? That's my new catch-phrase, "watch how fast I don't care". Feel free to use it.
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[(speed*care)^-2]
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That's because the heavier ball has more inertia. Inertia is proportional to mass, gravity isn't. Scroll up and see what I wrote about parachutes.
No, it really is just because the ball filled with water had greater mass. Also, what you said about parachutes in your earlier example simply confirms that.
The speed that a parachute falls at is given by the equation SQRT(2.m.g/Rho.Cd.A) and you can clearly see that greater mass will cause it to fall faster.
Notice that in that equation if you hold gravity and drag constant, the only thing that will change the speed is the mass.
Regards
Badboy
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Yet the Brewster seems to defy all of that. Not sure why we developed the P51. :headscratch:
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So do we all agree that gravity is not proportional to mass?
You don't know what proportional means? It's basic multiplication. It's why the Sun has more gravitational force than the Moon.
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Yet the Brewster seems to defy all of that. Not sure why we developed the P51. :headscratch:
Post your data. Show us what is wrong with the Brewster.
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Yet the Brewster seems to defy all of that. Not sure why we developed the P51. :headscratch:
Have you tested it? You post with the confidence that ought to be backed by data, yet is uninformed.
How do I know? Because I have tested it. The Brewster does nothing unexpected. In power on and power off tests it decelerates much, much faster than the Fw190D-9 regardless of the initial speed of the test.
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Have you tested it? You post with the confidence that ought to be backed by data, yet is uninformed.
How do I know? Because I have tested it. The Brewster does nothing unexpected. In power on and power off tests it decelerates much, much faster than the Fw190D-9 regardless of the initial speed of the test.
Correct. What it does do well is hold itself stable against its own torque as the speed falls off in a straight zoom. This is an important part of getting the most out of a zoom, that is why the P38 is probably the best zoomer, even though it doesnt have the best thrust/weight or the lowest drag airframe.
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Have you tested it? You post with the confidence that ought to be backed by data, yet is uninformed.
How do I know? Because I have tested it. The Brewster does nothing unexpected. In power on and power off tests it decelerates much, much faster than the Fw190D-9 regardless of the initial speed of the test.
Have you posted your test data?
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Have you posted your test data?
450-400 power on
47.56: Fw190D-9
7.56: Brewster
400-350 power on
NA.NA: Fw190D-9
11.84: Brewster
350-300 power on
NA.NA: Fw190D-9
29.53: Brewster
450-400 power off
6.69: Fw190D-9
3.51: Brewster
400-350 power off
7.44: Fw190D-9
5.18: Brewster
350-300 power off
8.38: Fw190D-9
5.62: Brewster
300-250 power off
9.47: Fw190D-9
6.87: Brewster
250-200 power off
10.41: Fw190D-9
8.31: Brewster
200-150 power off
10.43: Fw190D-9
9.50: Brewster
Fw190D-9 retains energy much better than the Brewster.
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You don't know what proportional means? It's basic multiplication. It's why the Sun has more gravitational force than the Moon.
No I know what proportional means. And I said that gravitation is proportional to mass but not gravity. Scroll up.
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No, it really is just because the ball filled with water had greater mass. Also, what you said about parachutes in your earlier example simply confirms that.
The speed that a parachute falls at is given by the equation SQRT(2.m.g/Rho.Cd.A) and you can clearly see that greater mass will cause it to fall faster.
Notice that in that equation if you hold gravity and drag constant, the only thing that will change the speed is the mass.
Regards
Badboy
Greater mass causes things to fall faster because inertia is proportional to mass. Thus the greater inertia the more drag required to slow an object. Not because mass changes gravity, it doesn't.
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:o :o :o :o :o :o :o :o :o :o :o
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In a vacume on Earth all objects will accelerate at 32 feet per second per second due to gravity regardless of mass, shape or size.
As soon as you add air there's a force against which the object must fall. An object that's lighter than air won't fall at all and may actually rise. As objects become heavier they fall faster and faster. This has nothing to do with inertia. The heavier object falls faster because the force of air resitance is the same against two similarily sized and shaped objects regardless of their weight so that force is less of a factor against a heavier object and more of a factor against a lighter one.
Once two objects of similar size and shape, but of differing weights are in motion at the same speed, the one with more weight has more inertia for the same reasons as stated above. The forces acting to slow it down are less a factor than they are against the lighter object.
Weight will cause an object to accelerate quicker in air whereas inertia will keep a heavier object in motion longer than a lighter one.
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No I know what proportional means. And I said that gravitation is proportional to mass but not gravity. Scroll up.
Gravity and gravitation refers to the same thing.
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The heavier object falls faster because the force of air resitance is the same against two similarily sized and shaped objects regardless of their weight so that force is less of a factor against a heavier object and more of a factor against a lighter one.
The force is less of a factor against the heavier object why? Because a heavy object in motion requires more resistance to slow it down. That's inertia my friend.
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Gravity and gravitation refers to the same thing.
When I refer to gravitation I'm refering to gravitational field, ie. your example with the moon producing weaker gravity than the earth. The force of a physical body's gravitational field is proportional to it's mass. That does not apply to what were talking about because we're not talking about how much of a gravitational field an airplane generates.
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When I refer to gravitation I'm refering to gravitational field, ie. your example with the moon producing weaker gravity than the earth. The force of a physical body's gravitational field is proportional to it's mass. That does not apply to what were talking about because we're not talking about how much of a gravitational field an airplane generates.
So if I have a 1 lb ball and a 10 lb ball and I want to give them equal acceleration do I apply the same amount of force to both or does the 10 lb ball require more force given it's greater inertia?
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All of this is why the language of physics is mathematics, not prose.
The relevant equation of motion was posted a long way back by, I think, Badboy: a = g - D/m. You don't have to argue about terminology. The equation says it all.
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So if I have a 1 lb ball and a 10 lb ball and I want to give them equal acceleration do I apply the same amount of force to both or does the 10 lb ball require more force given it's greater inertia?
That's the thing about gravity; it acts upon objects equally regardless of size or mass (unless you get into astronomical sizes). So the 1 lb ball and the 10 lb ball will both accelerate at exactly the same rate, however you would have to apply a 10 lb force to counteract the gravity of the 10 lb ball, while the 1 lb ball only requires 1 lb.
There are four forces acting upon an aircraft in a vertical climb:
Gravity: A constant 1G applies a force towards the ground that equals the weight of the aircraft.
Drag: A variable that depends on speed and the aerodynamic properties of the ariceaft.
Thrust: A variable that depends on engine power, prop efficiency and other factors.
Kinetic energy: The stored energy (inertia) of the aircraft; speed.
If the thrust is insufficient to overcome gravity and drag, the aircraft will lose kinetic energy until it is stationary and starts to fall. Gravity is constant, but drag is reduced by the square of speed. In other words when you reduce speed by half, drag is reduced to one-quarter.
The reason why kinetic energy/inertia is important is because WWII fighters have so little thrust that inertia becomes the main source of energy to overcome drag. Gravity is equal no matter the size of the aircraft so the only factors that will make a major difference between two aircraft is inertia and drag. The aircraft with the best weight to drag ratio is the better zoomer unless there is a major difference in thrust to weight ratio.
Throw a 1 lb steel ball and a 1 lb cotton ball into the air at the same speed. The steel ball will go higher due to its better aerodynamic properties; weight to drag ratio. Glue on a rubber band powered prop on both... Steel ball will still go higher.
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I love you guys. :)
(http://i1318.photobucket.com/albums/t646/FLOOB1/8DFB3B86-F049-407D-B21A-45ED959F1560_zpsiuxnsvnk.png)
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I love you guys. :)
(http://i1318.photobucket.com/albums/t646/FLOOB1/8DFB3B86-F049-407D-B21A-45ED959F1560_zpsiuxnsvnk.png)
(https://dl.dropboxusercontent.com/u/26232318/1459224_485728394792732_1190963333_n.jpg)
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That's the thing about gravity; it acts upon objects equally regardless of size or mass (unless you get into astronomical sizes). So the 1 lb ball and the 10 lb ball will both accelerate at exactly the same rate, however you would have to apply a 10 lb force to counteract the gravity of the 10 lb ball, while the 1 lb ball only requires 1 lb.
There are four forces acting upon an aircraft in a vertical climb:
Gravity: A constant 1G applies a force towards the ground that equals the weight of the aircraft.
Drag: A variable that depends on speed and the aerodynamic properties of the ariceaft.
Thrust: A variable that depends on engine power, prop efficiency and other factors.
Kinetic energy: The stored energy (inertia) of the aircraft; speed.
If the thrust is insufficient to overcome gravity and drag, the aircraft will lose kinetic energy until it is stationary and starts to fall. Gravity is constant, but drag is reduced by the square of speed. In other words when you reduce speed by half, drag is reduced to one-quarter.
The reason why kinetic energy/inertia is important is because WWII fighters have so little thrust that inertia becomes the main source of energy to overcome drag. Gravity is equal no matter the size of the aircraft so the only factors that will make a major difference between two aircraft is inertia and drag. The aircraft with the best weight to drag ratio is the better zoomer unless there is a major difference in thrust to weight ratio.
Throw a 1 lb steel ball and a 1 lb cotton ball into the air at the same speed. The steel ball will go higher due to its better aerodynamic properties; weight to drag ratio. Glue on a rubber band powered prop on both... Steel ball will still go higher.
That's quite an answer for a rhetorical question. :lol
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That's quite an answer for a rhetorical question. :lol
Because you were referring to FLOOB's post about gravity, your "rhetorical" question gave the wrong impression. Gravity accelerates all objects equally regardless of mass.
So when it comes to how gravity affects objects...
So if I have a 1 lb ball and a 10 lb ball and I want to give them equal acceleration do I apply the same amount of force to both or does the 10 lb ball require more force given it's greater inertia?
... is wrong. The answer is: No! ;)
However, to counteract the gravity on those objects you'd have to apply a force equal to their respective weight. I.e. 1 lb vs 10 lb.
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Gravity accelerates objects of different mass at the same rate of acceleration. In order to do that the force is necessarily proportional to the mass.
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Gravity accelerates objects of different mass at the same rate of acceleration. In order to do that the force is necessarily proportional to the mass.
No. According to general relativity, gravity is an attribute of curved spacetime instead of being due to a force propagated between objects. There is no gravitational acceleration, in that the proper acceleration of objects in free fall are zero. Rather than undergoing an acceleration, objects in free fall travel along straight lines (geodesics) on the curved spacetime.
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All of this is why the language of physics is mathematics, not prose.
The relevant equation of motion was posted a long way back by, I think, Badboy: a = g - D/m. You don't have to argue about terminology. The equation says it all.
A PhD and 25 years experience teaching this to College students and we might as well be discussing fairies at the bottom of the garden :rolleyes:
Badboy
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A PhD and 25 years experience teaching this to College students and we might as well be discussing fairies at the bottom of the garden :rolleyes:
Badboy
Do fairies fall faster in a vacume and if so which works best, Oreck or Hoover?
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The fairy force is transmitted by farions. CERN is looking for those after they fully nail down the Higgs boson.
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I love you guys. :)
(http://i1318.photobucket.com/albums/t646/FLOOB1/8DFB3B86-F049-407D-B21A-45ED959F1560_zpsiuxnsvnk.png)
Head now to Eden. Yay, brother.
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What got me mostly into fairies is that I've been finding lots of fairy evidence...
I'm Lydia and I'm a fairy scientist.
http://www.youtube.com/watch?v=akk5EvTMGKo
A young lady with a bright future :aok
Badboy
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http://www.youtube.com/watch?v=akk5EvTMGKo
A young lady with a bright future :aok
Badboy
Or abject failure and a life of drugs and alchohol.
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Too bad we cannot attribute it to Casimir force.
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But what about the effects on/of a zoom climb into a stiff headwind? ( L.O.L...)
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Nope. Wrong. With the same air resistance both objects will fall at the same rate, regardless of their mass. Galileo supposedly did an experiment by dropping two balls of differing weights from the top of the leaning tower of Pisa, and both balls hit at the same time.
Galileo is often cited in theads like this one, and almost always in support of fuzzy logic regarding what happens to aircraft during a dive or a zoom. While it is not certain that Galileo actually carried out this experiment, if he had he would not of obtained the results that are widely reported. Just out of curiosity I investigated this a little more. I carried out the calculations in two different ways, firstly by writing the equations of motion as differential equations and solving them by direct integration and also by writing a high frequency simulation and comparing the results.
Firstly I used the calculations to verify the experiment I posted earlier (scroll up to see the video) and then to make predictions about what would have happened if Galileo had carried out the experiment. Assuming Galileo really wanted to see the influence that weight had on falling objects it makes sense that he would have used two similar objects of different weights and cannon balls would have been an obvious choice. Picking them as far apart in weight as possible, so that any difference would be highlighted is also an obvious choice, and in those days 6lb and 36lb iron cannon balls would have been available. If dropped from 183ft above the ground, when the 36lb ball struck the ground the 6lb ball would still be 1ft 4 inches in the air. Sine the 36lb ball was only just over 6 inches in diameter, a difference of 1'-4" should have been easy to see, if not so easy to measure.
But if only Galileo had a taller tower. If the same two cannon balls were dropped from the Empire State Building which is a little less than seven times taller, when the 36lb ball hit the ground, the 6lb ball would still be 48ft 5 inches in the air. Which means the heavy ball would have landed while the lighter one was just passing the windows on the 5th floor... Galileo would certainly have noticed that :)
Perhaps Galileo did spot the difference, which may be why he never described the experiment himself.
The fact is that if we want to know how aircraft perform in a dive or a zoom Galileo's alleged experiment does not help us. Newton on the other hand was born the same year that Galileo died, and Newton's laws are much more helpful.
Regards
Badboy
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They do not teach that anymore. When the two balls were dropped, the slightly heavier ball hit first. But it was not of enough distinction that the observers below could tell. Source: High School Physics class, year 2000.
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Did Galileo ever drop anything which had powered flight?
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But it was not of enough distinction that the observers below could tell.
Not a convincing explanation because I think most people could spot a 1'-4" difference, particularly since the balls were a lot smaller than that, so it would have been quite noticeable.
Even with the ping pong balls my students used, falling just over 8ft the difference was 4 to 5 times the diameter of the balls. It is easy to see the heavy ping pong ball pulling ahead in the video, it would have been much easier to see the heavy cannon ball pulling ahead in Pisa because the drop would have taken longer and the gap would have been four times bigger.
I suspect the difference is minimized in high school deliberately to help make explanations easier/simpler. Unfortunately that can cause the sort of confusion we have seen here.
Regards
Badboy
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Did Galileo ever drop anything which had powered flight?
Exactly, you can't use a dubious ballistics experiment to draw conclusions about atmospheric flight in high powered aircraft.
Badboy
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Galileo used balls of various weights rolling down inclined planes. Their rate of acceleration was easier to time.
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The reds always to try to nail my wingman Bozon too.
The fairy force is transmitted by farions. CERN is looking for those after they fully nail down the Higgs boson.
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Galileo used balls of various weights rolling down inclined planes. Their rate of acceleration was easier to time.
How ever he did it, his conclusion still leads people to believe that when you drop two objects the weight won't affect how they fall.
The example I gave earlier shows that if you dropped 6lb and 36lb cannon balls from the Empire State building the heavy one would hit the ground while the lighter one was still passing the 5th floor. That is a very different image, with a drop of 1250ft the balls land with a separation of more than 48ft that's 96 times the diameter of the larger ball over an altitude which for aircraft is fairly small.
That's why when real pilots discuss dives and zooms the weight of the aircraft is an important consideration. It is important because for atmospheric dynamics the mass of an object really does matter.
Regards
Badboy
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I have been told that the ballistic properties of fighter airplanes are really minor factors compared to its ratio of thrust to weight and drag as long as the engine is running, to the point that for example, a zoom climb from 400 TAS in a Pony with 25% fuel ought to be higher than a zoom from 100% fuel Pony under the same conditions, because the thrust/weight advantage more than makes up for the "ballistic" advantage of having more weight. Is that true?
How ever he did it, his conclusion still leads people to believe that when you drop two objects the weight won't affect how they fall.
The example I gave earlier shows that if you dropped 6lb and 36lb cannon balls from the Empire State building the heavy one would hit the ground while the lighter one was still passing the 5th floor. That is a very different image, with a drop of 1250ft the balls land with a separation of more than 48ft that's 96 times the diameter of the larger ball over an altitude which for aircraft is fairly small.
That's why when real pilots discuss dives and zooms the weight of the aircraft is an important consideration. It is important because for atmospheric dynamics the mass of an object really does matter.
Regards
Badboy
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I have been told that the ballistic properties of fighter airplanes are really minor factors compared to its ratio of thrust to weight and drag as long as the engine is running, to the point that for example, a zoom climb from 400 TAS in a Pony with 25% fuel ought to be higher than a zoom from 100% fuel Pony under the same conditions, because the thrust/weight advantage more than makes up for the "ballistic" advantage of having more weight. Is that true?
No, it is not true.
Let's have a look at the math again.
For a ballistic zoom the acceleration would be:
a = -g - D/m
For a power zoom the acceleration would be:
a = -g + (T-D)/m
In both cases if you keep everything constant but the weight the heavier aircraft will zoom higher.
Let's take a closer look at your example of the two P51s in a vertical zoom at 400mph with one at 100% fuel and one at 10% fuel. Putting in values for gravity, mass, thrust and drag and calculating the deceleration for each, then using those values with the 400mph start speed we can calculate the time for each aircraft to slow to 150mph. Then we can use those times to calculate the distance zoomed during that time. What happens in both cases is that the heavier aircraft has less deceleration so it zooms for longer and zooms higher. In the first case with no power the heavier aircraft zoomed 180ft higher than the lighter one. Under maximum power of course both aircraft zoomed higher than in the first example but the difference between them was less at 140ft.
That's a difference in zoom of between 4 and 5 aircraft lengths just based on fuel load. Factor in dissimilar aircraft with big weight differences and different props and drag and the situation gets more complicated but when you have heavy American aircraft with powerful engines and paddle blade propellers the difference would be even greater in favor the heavy aircraft to the extent that it would have been tactically significant both in zooms and dives.
I can't recall specific examples right now, but I'm sure I have read a number of anecdotal accounts by WWII pilots that verifies that.
Regards
Badboy
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Okay. When I tested zoom climbs from 400 from several different a/c in-game, almost all of them seemed to get 6000 feet and some change back, except the P-38 which got a full 7K.