Author Topic: Space (Read 1114 times)

Bodhi · « **Reply #15 on:** November 04, 2005, 11:21:13 AM »

ask Straiga, I think he said he was an astronaut too.... maybe it was a cosmonaut.

Sandman · « **Reply #16 on:** November 04, 2005, 11:27:05 AM »

If I fart in space would I move forward?

NUKE · « **Reply #17 on:** November 04, 2005, 11:34:08 AM »

If you were next to me, I'd move somewhere.

But the fart molecules probably would not be as dense.

ASTAC · « **Reply #18 on:** November 04, 2005, 01:12:45 PM »

Quote

Originally posted by Slash27
You watched 'Wing Commander':rofl

It was on cinemax last night believe it or not.

lasersailor184 · « **Reply #19 on:** November 04, 2005, 03:34:38 PM »

Yes Sandman.

Think of it like a canoe.

You are standing in a canoe on a quiet, silent lake. You are at one end of the canoe.

If you calculate your mass and center of gravity and the mass and CoG of the Canoe, you would find that the CoG of both of you and the Canoe rests on a single point.

Now run to the other end of the canoe. The canoe will have pushed itself in the opposite direction that you were running.

Now get to the other end of the Canoe and stop. Calculate the CoG of you and the canoe, and you'd see that it would be in the exact same spot as it was before.

Now take your farting in space example. The methane gas you give off will have a mass and a center of gravity. Now, when you fart, you will be pushed in one direction while the gas in the other.

But the whole time the CoG of both you and the gas will remain in the exact same spot. Even if you drift millions and millions of miles away (assuming no outside interferance), the CoG will be in the same spot.

g00b · « **Reply #20 on:** November 04, 2005, 03:51:09 PM »

You do not feel inertia in space. Only acceleration.

Chairboy · « **Reply #21 on:** November 04, 2005, 04:04:06 PM »

Don't be silly. A body in motion will tend to stay in motion, intertia works exactly the same in freefall as it does on the earth. If you start spinning, the centripetal force on your inner ear muscles will cause vertigo.

g00b · « **Reply #22 on:** November 04, 2005, 04:15:36 PM »

Go read up on centripital force.

http://www.answers.com/topic/centripetal-force

The only time you will feel anything is due to changes in velocity. Which by definition must involve an accleration.

g00b

Chairboy · « **Reply #23 on:** November 04, 2005, 04:17:38 PM »

I've got a better idea, with respect, why do don't YOU post what you disagree with here instead of sending everyone off on a goose chase.

Inertia does not disapear when you enter freefall.

2bighorn · « **Reply #24 on:** November 04, 2005, 04:37:34 PM »

Quote

Originally posted by g00b
Go read up on centripital force.
http://www.answers.com/topic/centripetal-force
The only time you will feel anything is due to changes in velocity. Which by definition must involve an accleration.

Inertia describes resistance of an object with mass to change of motion. Change of motion is simply change of velocity or change of motion's direction ie acceleration and/or angular acceleration.

g00b · « **Reply #25 on:** November 04, 2005, 04:40:09 PM »

You should still go read it. But I'll copy the relevant bits.

Quote

centripetal force
The centripetal force is the force pulling an object toward the center of a circular path as the object goes around the circle. An object can travel in a circle only if there is a centripetal force on it.

In the case of an orbiting satellite the centripetal force is its weight and acts towards the satellite's primary; in the case of an object at the end of a rope, the centripetal force is the tension of the rope and acts towards whatever the rope is anchored to.

Centripetal force must not be confused with centrifugal force. In an inertial reference frame (not rotating or accelerating), the centripetal force accelerates a particle in such a way that it moves along a circular path. In a corotating reference frame, a particle in circular motion has zero velocity. In this case, the centripetal force appears to be exactly cancelled by a pseudo-force, the centrifugal force. Centripetal forces are true forces, appearing in inertial reference frames; centrifugal forces appear only in rotating frames.

Centripetal force must not be confused with central force either.

Objects moving in a straight line with constant speed also have constant velocity. However an object moving in an arc with constant speed has a changing direction of motion. As velocity is a vector of speed and direction, a changing direction implies a changing velocity. The rate of this change in velocity is the centripetal acceleration. Differentiating the velocity vector gives the direction of this acceleration towards the center of the circle.

By Newton's second law of motion, as there is an acceleration there has to be a force in the direction of the acceleration. This is the centripetal force.

You'll note the use of the term acceleration. There are some formulas on the linked page if you want to know the specifics. Basically if you are in or on a rotating spaceship you are experiencing a continuous acceleration (centripetal acceleration). If the rotation speeds up or slows down or changes direction you are experiencing an acceleration(angular acceleration). If the spaceship starts to actually move in one direction or another you are experiencing acceleration (linear acceleration).

Any change in velocity (The vector giving the speed and direction of motion of any object) requires an accleration.

I'm not a physics teacher so I hope that all makes sence.

g00b

2bighorn · « **Reply #26 on:** November 04, 2005, 04:48:50 PM »

Quote

Originally posted by g00b
You'll note the use of the term acceleration. There are some formulas on the linked page if you want to know the specifics. Basically if you are in or on a rotating spaceship you are experiencing a continuous acceleration (centripetal acceleration). If the rotation speeds up or slows down or changes direction you are experiencing an acceleration(angular acceleration). If the spaceship starts to actually move in one direction or another you are experiencing acceleration (linear acceleration).

Any change in velocity (The vector giving the speed and direction of motion of any object) requires an accleration.

Quote

Inertia describes resistance of an object with mass to change of motion. Change of motion is simply change of velocity or change of motion's direction ie acceleration and/or angular acceleration.

Question for you. How does above explain your claim: "You do not feel inertia in space"?

Chairboy · « **Reply #27 on:** November 04, 2005, 04:51:00 PM »

With respect, when you said:

Quote

Originally posted by g00b
You do not feel inertia in space. Only acceleration.

then

Quote

Originally posted by g00b
I'm not a physics teacher so I hope that all makes sence.

became very clear already.

I suspect you may be confusing terms. Inertia is present no matter where you are, in space or on the ground.

Additionally, you seem to have forgotten about Coriolis force. In the example you gave, people walking on the outside rim of the station would feel not only the downward "pull" against the floor, but also a slight precession as a result of the constant "acceleration" against the floor as the wheel turned in a circle.

For example, if you pee into a urinal on a rotating space station, you need to aim slightly to the side of where you want it to hit because of coriolis. Once it leaves your body, the urine will want to continue along the path it started, but since the rest of the environment is "accelerating" in an arc, it will seem to traverse an odd path indeed.

If you want to know why I know this, well, I could tell you, but I'd have to kill you. Ooops, gotta run, time to take another cargo load up to The Wheel from Nellis.

Sandman · « **Reply #28 on:** November 04, 2005, 04:51:02 PM »

Quote

Originally posted by lasersailor184
Yes Sandman.

Think of it like a canoe.

You are standing in a canoe on a quiet, silent lake. You are at one end of the canoe.

If you calculate your mass and center of gravity and the mass and CoG of the Canoe, you would find that the CoG of both of you and the Canoe rests on a single point.

Now run to the other end of the canoe. The canoe will have pushed itself in the opposite direction that you were running.

Now get to the other end of the Canoe and stop. Calculate the CoG of you and the canoe, and you'd see that it would be in the exact same spot as it was before.

Now take your farting in space example. The methane gas you give off will have a mass and a center of gravity. Now, when you fart, you will be pushed in one direction while the gas in the other.

But the whole time the CoG of both you and the gas will remain in the exact same spot. Even if you drift millions and millions of miles away (assuming no outside interferance), the CoG will be in the same spot.

LOL... it's something to think about while I'm farting. Thank you for that.

g00b · « **Reply #29 on:** November 04, 2005, 05:03:13 PM »

"Question for you. How does above explain your claim: "You do not feel inertia in space"?"

I never claimed inertia is not present or non-existant.

Inertia is NOT a force. How can you feel something that is not a force?

I maintain....

You do not feel inertia in space. Only acceleration.

I'm done with this conversation.

g00b