Gravity physics

[DrPizza]

Originally posted by: Basse

Originally posted by: beansbaxter
The turn & slip indicator in an airplane (that little curved glass tube with the black ball in it) is a very simple and precise indicator of this. When that ball is at the low point of the curved tube, all is right with the world. Roll the airplane off level while keeping the nose on a point and that little ball always stays "down" with great sensitivity.

Speaking of airplanes, a different view on this topic.
Say your in a Concorde that can go halfway round the world without refueling. If you wanted to stay @ 80,000 feet the whole trip, you would have to keep the rudder at a constant slight downward position. Otherwise the altitude would increase as you go. (I have deliberately kept gravity out of the example).

(not to mention, you'd have to get permission to get the concorde off the ground!)

Unfortunately, you can't ignore gravity in this example though. That'd be like saying the space shuttle or satellites have to steer to keep in a circular (elliptical) orbit around the earth. In reality, the space shuttle is in freefall toward the earth. It's just that by the time it's fallen 1 millimeter closer to the earth, its "linear" path has taken it 1 millimeter farther away from the earth. If somehow you could get the space shuttle to "stop" at whatever altitude it flies at, the astronauts would be able to stand on a scale and measure their weight. (lower than on the surface though)

 

[jagec]

Originally posted by: Basse

Speaking of airplanes, a different view on this topic.
Say your in a Concorde that can go halfway round the world without refueling. If you wanted to stay @ 80,000 feet the whole trip, you would have to keep the rudder at a constant slight downward position. Otherwise the altitude would increase as you go. (I have deliberately kept gravity out of the example).

actually no...even with the rudder level, it will maintain the right altitude, because as it "climbs" into thinner air it loses a bit of lift and starts leveling out. That's where the whole "control the altitude with throttle, the airspeed with elevator" thing comes in.

 

[biostud]

Originally posted by: josphII
you are both wrong. if the system is truely frictionless the ball would oscilate back and forth

Maybe for a while but in the end it would stop, since it would not move against the gravity ie. goin back to where it started.

 

[Description]

it would not move against the gravity ie. goin back to where it started

It would.

 

[biostud]

Originally posted by: Description

it would not move against the gravity ie. goin back to where it started

It would.

It depends if it's stopped in the end 😛

And if it is then it should not transfer any energy to the block, but otherwise I concur, I was wrong (and it didn't hurt that much to admit it 😀)

 

[sabatcj]

Now everyone is assuming the the sphere is perfect. Just my .02

 

[jagec]

that was discussed, and it was concluded that the deviations from perfection were too small to make that much of a difference.