# Homework Help: Really hard physics problems

1. Jan 14, 2004

### tandoorichicken

I hate to be taking up so much board space today, but all my problems are so freakin difficult.

1. a) show that the kinetic energy of a satellite in circular orbit r about the earth is one half the magnitude of its gravitational potential energy.
b) what is its total mechanical energy?

2. Okay, I have to describe the picture in the book for this one: There is a wheel of r = 0.38m and m = 1.3kg and attached to that wheel from a cord is a 0.70kg block that is 1.2m off the ground.
a} If the block is released from rest, what speed will it have just before it hits the floor if there is no friction at the wheel's axis?
b) If there is friction on the axis, what is the frictional torque if the speed just before the block hits the floor is half of the speed it would have without friction.

2. Jan 14, 2004

### himanshu121

Write the formula for K.E ,Centripetal force Equation and P.E u will get the result Mechanical Energy= P.E+K.E