Aces High Bulletin Board
General Forums => Aces High General Discussion => Topic started by: fscott on January 29, 2001, 01:11:00 PM
-
If you answer this then you will help me understand the factor of weight pertaining to a plane's ability to dive and maximum dive speeds.
I understand that gravity on earth is 32 ft/sec. Ina vaccum all things will fall at this equal rate. But my concern is weight. Does an object continue to fall at a faster and faster rate in a vaccum? For instance, is there a maximum attainable speed based on an object's mass?
Simplify this. The moon is determined to be falling at a rate of 1/20 inch per sec. If it is continuing to fall at this rate, why doesn't it speed up and eventually hit the earth since space is a vacuum? Am I correct that the moon's mass has determined a maximum attainable rate of fall?
Again, only need one question answered ---> Will an object reach a maximum speed in a vacuum based upon it mass?
fscott
-
---> Or will it fall faster and faster and faster until it hits something or reaches an infinate speed?
fscott
-
I do not believe the moon is capable of gaining more speed at it's rate of descent to earth, because at the current stage in human evolution it is impossible for a human to bend over and kiss his bellybutton goodbye.
;-)
-SW
-
The reason I ask, and how it pertains to a plane's ability to dive: If we had a zero drag aircraft, I am wondering how weight would play a factor in it's dive? It seems that in a vaccum, weight would play no role in an object's acceleration in a dive. However, I am assuming that weight would play a role in an objects maximum attainable rate of fall, or maximum mph.
However, when thrust is added into the equation, weight then becomes a factor?
fscott
-
Acctualy the moon is falling at a rate of about 750 mph it just happens to be moving sideways at 2300 mph so it keeps missing the earth.
To answere your question yes it will keep accelerating at the same rate regardless of mass. Until light speed effects kick in.
To put it in a math perspective for you.
Force = Mass * Acceleration
Force would be the wieght of the object.
Velocity = Acceleration * Time.
Distance = Velocity * Time
Distance = Acclerations / 2 * Time * Time
HiTech
-
Your question is fairly simple fscott add up the total down forces which would be Weight + Thrust , now subtract out the current drag of the plane. The acceleration can be computed by the first equeation.
HiTech
-
HiTech stated:
"To answere your question yes it will keep accelerating at the same rate regardless of mass. Until light speed effects kick in."
Ok, then tell me why the moon does not speed up it's rate of falling to the earth? It is in a vacuum. If it continues to fall at a faster rate, then I would assume it would also have to keep speeding up sideways to prevent hitting the earth. We know the moon is not falling faster, so my question is why isn't it falling at a faster and faster rate until as you say hits the speed of light?
fscott
-
Forward momentum has no effect on an object's rate of descent. So what keeps the moon from falling faster and faster and faster. I would assume it's mass keeps it at a steady maximum rate of fall?
fscott
-
Because the 1/10 inch your refering to, not sure if that number is correct, is do to the fact that the moon is slowing down in it's orbit priamarly do to the energy lost creating tides.
HiTech
-
Best way to picture orbital effects is visualize bullet drop, Now what would happen if you shot bullet fast enough,(assume no drag) so that its arc of drop would = the curvature of the earth. Note the bullet is constantly accelerating to the earth.
HiTech
-
start by seperating weight and mass - weight is a result of gravity on mass - mass is harder to define
the answer to your question involves newtons 2nd f=ma
all objects regardless of mass are accellerated at the same rate due to gravity - which as you mentioned is 32 feet per second - except that value is squared
you have to take into account wind resistance in this example though because you are on earth and it is a real factor when dealing with planes in a dive - because as the body accellerates it experiences more wind resistance until it finds equalibrium - the concept is called terminal velocity - a heavier object(more mass) might accelerate toward the earth faster initially due to its ability to negate some wind resistance ....maybe thats what you are looking for i dont know. does that anwser it? if not lemme know
-
I think I'll insert a little here......"Why isnt the moon accelerating to light speed to crash into the earth?" You have to think of all the forces acting on the moon, not just the earths gravitational pull, How about the force generated buy the moons own mass in traveling an orbit (centrifugal force), this would counter-act some of the earths G-force that is acting upon it, as well as the C-force of traveling around the sun (although probably negligable in this case). You also have to take into consideration on top of all this the relationship of the masses involved to the forces exerted, in our case the moon isn't going to hit us anytime soon, it would take alot more force and distance to get that sucker moving at an even remotely acceptable speed.
Or maybe I'm just crazy.
-
Originally posted by AcId:
How about the force generated buy the moons own mass in traveling an orbit (centrifugal force)
i think that is correct except i believe the force would be centripetal - since centrifugal force is really kind of illusion of the angular momentum caused by a center seeking object - dont forget the earth isnt just attracting the moon it goes both ways - F=g(m1)(m2)/r sq.
[This message has been edited by mrfish (edited 01-29-2001).]
-
Thats it!!!! centripetal.....i forgot what it was and just used centrifugal. (http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif)
My brain hurts now.
-
Here's how it works according to my limited understanding. Everything in the universe exerts a gravitational force on everything else; this force is a function of the mass of the subject (the exerter) and the distance to the object (and I imagine it ain't a linear relationship. I have no idea what the equation is, but it'll probly be along the lines of accel=mass/distance^3; someone correct me please. edit: better yet, just steal MrFish's calcs). The mass of the object here is irrelevant: a cruise ship full of overweight retirees and a baseball will -- if held at the same distance to the earth's center -- accelerate towards the earth at the same rate.
This is the reason for the apocryphal story of Galileo dropping two weights from the leaning tower of Pisa, and showing how both hit the earth at the same time.
I said the mass of the object was irrelevant; that's true, but you have to understand that the object functions as a subject as well. So, while the earth has far more mass than the moon, and the moon goes in orbit around it, the earth is being shaken around by the moon's gravity (cf., e.g., tides).
Generally, though, the gravitational measurements we play with involve such disproportionate forces that we ignore one side of the equation as insignificant (even if that cruise ship was serving fried chicken, it still wouldn't move the earth much), and indeed, Kepler's fairly accurate equations for solar orbits do not take into account the mass of the satellites.
[This message has been edited by Dinger (edited 01-29-2001).]
-
The way I get it. Because its moving side ways at almost 3 times the speed its falling.The two speeds cause it to orbit in the same position, instead of moving closer or falling.
Its been a long time since I read anything on the solar system. Basicly I'm winging it. Don't even know if I'm close to the rite answer. (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
-
Er, guys, the moon is moving toward earth, and one day, will crash into it,..if memory serves me correct, I think the Discovery channel said something like 10.2 billion years, or something astronomical number...
Correction, see post below...thats the Earth moving towards the Sun?
[This message has been edited by Ripsnort (edited 01-29-2001).]
-
Ummm...Off topic? Hee Hee....just kidding HT!! (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
-
the moon is moving away from the earth - not toward .....about 4 cm per year
it'll take about 15 x 10 9th years - we will be toast in about 1/2 that time anyway and even if we were around the orbit would steady out at about 2x the present distance
-
Thank you, AWAY, not towards...man, the mind is the first thing to go, and the 2nd is...hmm, I forget...
As far as the orbit decaying, actually currently due to the tidal
forces between the Earth and moon the distance between is
increasing. The spin of the Earth is literaly pulling the moon faster
which causes it to orbit farther away. It will be far into the future
before the moon tidal locks the Earth and starts to decay. We'll have
to worry about being burned up by the sun first!
[This message has been edited by Ripsnort (edited 01-29-2001).]
-
Cc
The moon will eventually escape earth's gravity. As it moves away, the earth's gravity pulls it back in which in turn makes the moon's gravity pull the ocean towards it creating the tides.
The earth will be consumed when the sun becomes a red giant WAAAY before the moon escapes earth's gravity though.
-
someone correct me if i am wrong but i dont believe the earth is going to crash into the sun due to gravity - there are at least 3 bodies affecting the calculation of that and i think that might be one too many to get an accurate prediction -
in 6 bil yrs though the sun will be a red giant and its fuel will be expended in about 10 billion yrs - so really the sun will come to us
run!!!!!!!!!
-
Originally posted by fscott:
Again, only need one question answered ---> Will an object reach a maximum speed in a vacuum based upon it mass?
fscott
The max velocity is independent of the mass. You all remember that in a vacuum a feather will fall just as fast as a 1,000lb ball of led. Acceleration due to gravity it just that. It has nothing to do with mass. EVERYTHING in a vacuum accelerates at 32.2ft/sec/sec on earth. It will NEVER reach a maximum speed with out the presence of some drag/force. A body in motion will remain in motion unless acted upon by and out side force. Terminal velocity is what I think your looking for and that is based on drag (the outside force). Everything has a terminal velocity based on it's Coefficient of drag (Cd). For a man it is roughly 160 mph. F=ma a is constant equaling 32.2ft/sec/sec. So to answer your question no it has nothing to do with mass it has to do with the gravitational constant in a vacuum. Put the object in a medium of some kind and you will have to take into account the shape/drag of the object.
PS Ooops Dinger already answerd you. (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif) You got it Dinger. (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif)
[This message has been edited by Jimdandy (edited 01-29-2001).]
-
Cc
The moon will eventually escape earth's gravity. As it moves away, the earth's gravity pulls it back in which in turn makes the moon's gravity pull the ocean towards it creating the tides.
The earth will be consumed when the sun becomes a red giant WAAAY before the moon escapes earth's gravity though.
An object in vacumm will attain .9999999 (add infinite number of 9's) of light speed. However, the amount of energy you must spend to get it to that speed is not only astronomical, but it also increases exponentially, as object gain mass the as they approach lightspeed. You must have infinite mass and infinite energy to push something TO lightspeed.
Nasa is researching into FTL (Faster than Light) technology..some of the ideas are really wild.
-
Gee, this is fun. I want to answer the moon question..."Why doesn't the moon accelerate to infinity?"
As everyone has pointed out, there are essentially 2 forces acting on the moon. The first is the attractive force between the Earth and Moon or simply weight. The second is the centrifugal force acting on the moon due to the elliptical orbit (it has to keep changing direction) which points away from the center of the orbit. Now lets sum the forces and see what we get, remembering that the centrifugal force must equal the attractive force for a stable orbit.
First, F=m*a. Now for a circular motion, a=v^2/r where r = radius of the cirle. Thus, Fcentrifugal = m*V^2/r. The attractive force or law of gravitation is Fgravitation = G*m1*m2/r^2 where m1 = moons mass and m2 = earth's mass. So, we let Fcentrifugal = Fgravitation which gives
Mmoon*V^2/r = G*Mmoon*Mearth/r^2
Simplifying gives
v = sqrt(G*Mearth/r)
Lets try some numbers,
G = 6.67*10^-11 m^3/Kg/s^2
Mearth = 5.972 *10^24 Kg
rmoon = 384,400,000 m
which equates to a moon orbital velocity of 1.02 Km/s (which is correct).
So, to sum up. The moon is constantly accelerating at v^2/r or .0027m/s/s. But there is a centrifugal force that opposes gravity that keeps it from going 9.8 m/s/s.
xmab
-
answer to the question why an object accelerating cannot reach any speed is more complex and needs solid physics masters course (which I had, hated, A-ed nevertheless and forgot immediately execpt this small burp ;-) I hope this e-mail will not be too heady.
Newton's physics is a "gross" simplification of reality (like any model BTW ;-) but it happens to hold very well @ speeds way below speed of light (up to 0.99c or so). The real formula for speed is not simply time*acceleration but it has further terms which were hellishly complex and funny enough, I sweat the details so go read it up. Basically if you take all the terms, Newton holds up to about 0.99c like I said and then all the other terms in the equations start to kick in and toejam gets weird. First: You get heavier and heavier the faster you get ;-) Literally since e=mc^2 as you know, because you start to build up such a huge amount of energy, your mass goes up so you have to pump even more E to accelerate. If you run the lim (not the fruit, it's a mathematical concept) on the whole thing, you'll figure out that you'll be never able to break speed of light. That formula and the limites were the nobel prize so don't expect to pick it up in an afternoon. Second: time (or rather lack thereof) start to behave ape-shit. Basically you loose the absolute meaning of time but it becomes all relative depending from where you measure stuff, you see the guys you left behind as progressing in their time much slower than they progress in their time. They see you progressing much faster. That's where all the weirdo sci-fi literature with kids coming 8 years back from alpha and finding their great^24-parents comes from. That's why it's all relative ;-)
The question about moon hitting earth I think was answered pretty well by hitech and the other bunch. I though also that moon is actually being decelerated by friction and solar wind. The tide thing confused me, I never heard that it slows the moon down but most of those things boil down to the problem of "multiple masses" and that leads quickly to systems of stiff differential equations and our computing power going "poof" due to the rounding errors. Then basically nobody really has an answer what is cause and what is effect (and as Heidegger said for those who care: "cause and effect and time are just convienent non-existent crutches that our counciousness pulls over reality like a glove to make it accessible to our minds". Pretty heavy stuff, he ;-)
Lastly: HiTech, I really mind you getting me and 2 of my 308 buddies killed in a melee over city yesterday night. If you have to fly a spit well, don't make it so blatantly obvious. Give dweebs a chance next time ... ;-)
-
sorry xmab, I beg to differ, there is no force opposing the gravity. The vel of the moon tangentail to it's orbit is just changing the direction that gravity is working on the moon, i.e. the moon is constantly falling and accelerating at the rates you specified it just keeps missing the earth. If the moon was not moving, and could pass threw the earth it would fall and come out the other side at the same hieght it started from. This is in ensence what's going on in an orbit except with it's tang. vel to the earth it's ruberband motion turns into one contiuous arc.
HiTech
-
Picture a bullet fired horizontally. It is affected by gravity, and eventually strikes the earth. Now picture another bullet fired horizontally. This time it is fired from an Hispano 20mm, and is unaffected by gravity, reaches escape velocity and eventually leaves the solar system.
(http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
-
HiTech,
Now we have a really interesting question. "Is centrifugal force real?"
As you know, it is really a phantom force. That is, there is no physical construct for it. However, mathematically it exists.
I agree completely with your explanation. It is physically correct. However, how do you explain the limiting case for centripetal acceleration in the moon's case? Is it completely due to the initial condition of the moon's velocity (that is, why hasn't the velocity changed during the existence of the solar system)? Or is the problem in equilibrium due to the balance of weight and centrifugal forces as I have argued?
I submit that my equations predict the limiting tangential velocity for the moon and can predict the orbital velocity for any given radius. Thus mathematically, the notion of centrifugal force is correct, even if there is no physical force that you can feel.
In a way, we are arguing about semantics. But the mathematics are correct and do predict physical experiment.
xmab
-
My head hurts.
Fury
-
I think Fscott should share his "stash" (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
NUTTZ
-
"There are billions and billions of stars..." (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif)
Picture a spaceship flying over. You can see thru the spaceship. Inside is a clock that counts by bouncing a laser between to pieces of glass. Now trace the path of the laser as the ship flies over head. Which clock is slower retaliative to the observer on the ground the observers or the spaceships.
There is a train traveling at you. Which direction in the light spectrum is the light on the front of the train shifting toward. Which side of the spectrum is it going to if traveling away from you.
What would happen if the earth stopped rotating. Would we feel a stronger or weaker gravitational pull? What would happen if it spun faster. Would we fly off?
How many licks does it take to get to the tootsie roll center of a tootsie pop. (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif)
The last question is the real kicker. (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif)
[This message has been edited by Jimdandy (edited 01-29-2001).]
-
This is all irrelevant... in the year 1999 the moon is going to be ripped out of Earth's orbit by a nuclear mishap aboard one of our moonbases, and will be sent plummeting through...
huh? 2001?
Never mind.
-
Originally posted by hitech:
sorry xmab, I beg to differ, there is no force opposing the gravity. The vel of the moon tangentail to it's orbit is just changing the direction that gravity is working on the moon, i.e. the moon is constantly falling and accelerating at the rates you specified it just keeps missing the earth. If the moon was not moving, and could pass threw the earth it would fall and come out the other side at the same hieght it started from. This is in ensence what's going on in an orbit except with it's tang. vel to the earth it's ruberband motion turns into one contiuous arc.
HiTech
not to agree for the sake of agreeing but this is closest to what you would get if you plot it in a force diagram
- the centripetal force (as mentioned previously there is no centrifugal force)produces a vector (again direction and magnitude should be considered not just meshing formulae)which points adjacent to the body's path
- the second vector is of course the attraction due to gravity
conclusion? plot it and add the vectors - the resultant produces what is described above-
-
Not so much semantics as just a physical way of looking at things. Math wise for circular orbits it's much easier your way. But now try explaining to some one an extreme elliptical orbit with centrifugal force.
And as to your why hasn't the Vel of the moon changed, I submit it is changing constantly, depends if you view Vel as speed and direction or just speed. I've been doing this simming stuff to long, and it is almost impossible for me to view Vel,And force in any other terms than instantaneous vectors.
I do so love this stuff.
On a side note was debating if a circle is an ellipse, I can't remember if an ellipse definition is 2 unique points or 2 points.
HiTech
[This message has been edited by hitech (edited 01-29-2001).]
-
Actually an elliptical orbit is impossible... I think what you mean is a conic section.
-
Hang sits under a knit apple tree contemplating these postulations.
An apple falls, hits Hang on the head.
Hang rubs the knot on his head.. gets an idea.. loads up AH on the laptop; goes to mission screen and plots a mission to destroy and capture all knit apple trees.
(http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
-
No one reads my stuff. (http://bbs.hitechcreations.com/smf/Smileys/default/frown.gif) Someone answer mine. (http://bbs.hitechcreations.com/smf/Smileys/default/frown.gif) I feel so insignificant. I'm a wall flower on the BB of AH. (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif) LOL!
-
Ellipse:
http://observe.ivv.nasa.gov/nasa/education/reference/orbits/orbit_sim.html (http://observe.ivv.nasa.gov/nasa/education/reference/orbits/orbit_sim.html)
HiTech
-
OH MY COD!!...RUN, HIDE!!..WERE ALL GONNA DIE!!
Swamp
-
Cool,
Finally a thread that a geek like me can enjoy!
Nice link HT...ellipses are cool (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
I believe I understand our differences in terms. You probably are thinking in Cartersian coordinates. While I am assuming circular orbit and polar coordinates. If you think in polar or rotational coordinates than the moon's velocity is constant (for a simplified circular orbit and even as a vector). If you think in Cartesian coordinates than the velocity vector's direction is always changing (but not its magnitude).
Ellipitical orbits are certainly more complicated and require one to sum the forces in orthogonal directions to predict the motion.
Aren't you supposed to be working on 1.06? (Hehe).
xmab
-
ok JIMDANDY
since i have already geeked out all day and wasted tons of co. time i think i will take a stab at it:
Picture a spaceship flying over. You can see thru the spaceship. Inside is a clock that counts by bouncing a laser between to pieces of glass. Now trace the path of the laser as the ship flies over head. Which clock is slower retaliative to the observer on the ground the observers or the spaceships.
- the clock on the space ship would seem slow relative to the clock on the ground though each would operate the same in their referential frame (the speed of the spaceship would have been nice)
There is a train traveling at you. Which direction in the light spectrum is the light on the front of the train shifting toward. Which side of the spectrum is it going to if traveling away from you.
- toward the blue end of the spectrum and away the red end
What would happen if the earth stopped rotating. Would we feel a stronger or weaker gravitational pull? What would happen if it spun faster. Would we fly off?
- no gravity has nothing to do with it everything would remian the same (execpt of course weather)
EDIT: oops i meant rotation has nothing to do with it - yes gravity play a small part (http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif)
How many licks does it take to get to the tootsie roll center of a tootsie pop.
- 22 1/2
(http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif)
[This message has been edited by mrfish (edited 01-29-2001).]
-
Mass is like the stuff somethings made of and gravity is whay happens when you drop stuff!
Yeager (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
-
Ok one more. Which way does the US lunch it's rockets.
A. With the direction of rotation of the earth and why.
B. Against the direction of rotation and why.
C. None of the above and why.
Does a flash light generate thrust. Yes or no and why.
BTW mrfish you think your sooooooooo smart! The tootsie roll one is WRONG WRONG WRONG mister! It should be... (drum roll) The world may never know! So there. (http://bbs.hitechcreations.com/smf/Smileys/default/tongue.gif) Grumble grumble smart ass... grumble... know it all grumble. (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif)
[This message has been edited by Jimdandy (edited 01-29-2001).]
-
yeah yeah jim (http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif)
with rotation i imagine
-
Originally posted by mrfish:
yeah yeah jim (http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif)
with rotation i imagine
Yep. The earths rotation can be used to sling shot the rocket into orbit.
Sorry mrfish I added one after you replied.
[This message has been edited by Jimdandy (edited 01-29-2001).]
-
niether over the pole , reason shortest path to russia hehe.
-
I stand corrected (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
-
do you want me to scan my notes deriving kepler's laws all from F=ma?
its probably about 8 pages
-
Dang mrfish I'm got to thinking about this and play with the vectors and I have to make an corrction.
If you had a scale weighed an object at the poles you would get it's true weight Wt=Gmme/R^2. Wt=true weight, G= gravitational constant m= mass of the oject, me= mass of the earth. Now if you went to the equator you would have to take into account the centripetal force mv^2/R. Thus if you stoped the earth we would actually see a small increase in weight on the scale. G is still constant but are wieght at the equator would be slightly more.
Originally posted by mrfish:
ok JIMDANDY
since i have already geeked out all day and wasted tons of co. time i think i will take a stab at it:
Picture a spaceship flying over. You can see thru the spaceship. Inside is a clock that counts by bouncing a laser between to pieces of glass. Now trace the path of the laser as the ship flies over head. Which clock is slower retaliative to the observer on the ground the observers or the spaceships.
- the clock on the space ship would seem slow relative to the clock on the ground though each would operate the same in their referential frame (the speed of the spaceship would have been nice)
There is a train traveling at you. Which direction in the light spectrum is the light on the front of the train shifting toward. Which side of the spectrum is it going to if traveling away from you.
- toward the blue end of the spectrum and away the red end
What would happen if the earth stopped rotating. Would we feel a stronger or weaker gravitational pull? What would happen if it spun faster. Would we fly off?
- no gravity has nothing to do with it everything would remian the same (execpt of course weather)
EDIT: oops i meant rotation has nothing to do with it - yes gravity play a small part (http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif)
How many licks does it take to get to the tootsie roll center of a tootsie pop.
- 22 1/2
(http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif)
[This message has been edited by mrfish (edited 01-29-2001).]
-
Dux is Right - sort of! Ellipses are indeed possible, though.
The link HiTech cited is the stating of Kepler's Laws of Planetary Motion.
An ellipse is in fact a conic section - as are circles, parabolas, and hyperbolas.
A useful link: Newtonian Gravitation and the Laws of Kepler (http://csep10.phys.utk.edu/astr161/lect/history/newtonkepler.html)
------------------
Rape, pillage, then burn...
[This message has been edited by PakRat (edited 01-29-2001).]
-
Originally posted by Ripsnort:
Er, guys, the moon is moving toward earth, and one day, will crash into it,..if memory serves me correct, I think the Discovery channel said something like 10.2 billion years, or something astronomical number...
Correction, see post below...thats the Earth moving towards the Sun?
[This message has been edited by Ripsnort (edited 01-29-2001).]
The moons also getting closer to Earth...by about 8 inches a year. (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
-DIng
-
Originally posted by Jimdandy:
The max velocity is independent of the mass. You all remember that in a vacuum a feather will fall just as fast as a 1,000lb ball of led. Acceleration due to gravity it just that. It has nothing to do with mass. EVERYTHING in a vacuum accelerates at 32.2ft/sec/sec on earth. It will NEVER reach a maximum speed with out the presence of some drag/force. A body in motion will remain in motion unless acted upon by and out side force. Terminal velocity is what I think your looking for and that is based on drag (the outside force). Everything has a terminal velocity based on it's Coefficient of drag (Cd). For a man it is roughly 160 mph. F=ma a is constant equaling 32.2ft/sec/sec. So to answer your question no it has nothing to do with mass it has to do with the gravitational constant in a vacuum. Put the object in a medium of some kind and you will have to take into account the shape/drag of the object.
B]
OK you were complaining that no one answers you so I will Jim (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif) You are right and maybe a little wrong...
I think you (or maybe I) was getting tied up in your wording. First acceleration is not a force...it is the result of a force working upon a mass. It is the change in an objects velocity (a vector quantity) of some object due a force which is being EXERTED upon that object. I believe that was what you were trying to say?
However, the acceleration (or change of velocity) of two objects via gravity IS affected by mass...since
F(gravity) = Gm(1)m(2)/r^2
and
F=ma
Now what this means is this: the acceleration of objects towards the Earth is around 32 m/s^2 at ground level BUT if you take the same object and try to measure the acceleration towards an object of a different mass, you get a different value. You also get a different value for acceleration at varying distances from the center of the Earths mass.
Yes this gets confusing and you may have been right, but got caught up in the wording. Dunno if this makes any more sense (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
-Ding
-
Originally posted by hitech:
And as to your why hasn't the Vel of the moon changed, I submit it is changing constantly, depends if you view Vel as speed and direction or just speed. I've been doing this simming stuff to long, and it is almost impossible for me to view Vel,And force in any other terms than instantaneous vectors.
I do so love this stuff.
On a side note was debating if a circle is an ellipse, I can't remember if an ellipse definition is 2 unique points or 2 points.
HiTech
[This message has been edited by hitech (edited 01-29-2001).]
Love this stuff too (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif) Velocity is a vector sum meaning it has both SPEED and DIRECTION. So I concur that the velocity of the moon is constantly changing. (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
And yes a circle is an ellipse...its just that the two focal points lie on top of one another.
-DIng
[This message has been edited by Dingy (edited 01-30-2001).]
-
Originally posted by Jimdandy:
If you had a scale weighed an object at the poles you would get it's true weight Wt=Gmme/R^2. Wt=true weight, G= gravitational constant m= mass of the oject, me= mass of the earth. Now if you went to the equator you would have to take into account the centripetal force mv^2/R. Thus if you stoped the earth we would actually see a small increase in weight on the scale. G is still constant but are wieght at the equator would be slightly more.
Whoa?? True weight? What is that?
Weight is nothing more than a measurement of forces upon some mass. Usually we use weight to indicate the force of gravity upon some mass.
Because the force of gravity is dependent upon the mass of the object you are measuring, the mass of the Earth (or whatever planet you are measuring on) and the distance the two centers of mass are from one another, you are also going to find different weights for an object depending upon which altitude (distance from the center of your mass from the center of the Earth's mass) you measure at.
You are right tho, the rotation of the Earth does have a minor effect of an objects weight due to centrifugal force (really just a resultant change in an objects rotational velocity).
-Ding
[This message has been edited by Dingy (edited 01-30-2001).]
-
what's wrong with....
Mass ?
-
Originally posted by Dingy:
The moons also getting closer to Earth...by about 8 inches a year. (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
-DIng
i have to disagree based on nasa's laser distance measuring experts as well as satellite observations between 1970 and today - curiously what are your sources?