Angular Momentum

1. Dec 17, 2004

Alkatran

We had a demonstration in physics, which I'm sure most of you have seen, of a wheel spinning very quickly maintaing it's orientation. (There is a string hooked to one end of the axle, and you expect the wheel to 'flop' downwards)

Now, I was just wondering what the math behind this is?

The spinning wheel has a high angular momentum in direction X while there is a torque from gravity in direction Y: after that...? This is definitely similar to it being difficult to slow an airplane rather than a ball.

2. Dec 17, 2004

NateTG

The spinning wheel is typically called a gyroscope, and the movement is referred to as precession.

I'm pretty sure that it's possible to work things out starting from linear momentum to see that there's a net torque on the wheel as a rigid object by, for example, looking at the necessary change in velocity of point masses along various places on the gyroscope to tilt the axle while the wheel remains spinning.

3. Dec 21, 2004

bionic_atom

F=force
m=mass
0=theta
I wanna say F=mdcos0 but I am not 100% sure, and in physics when we are not 100% sure we say were just guessing.