A daredevil is riding a motorcycle on the inside of a spherical metal cage of radius 9.7 meters. The total mass of the person and motorcycle is 79.2 kg. If he is to make a vertical circle within the cage at some constant speed, v, what normal force, in Newtons, does he feel at the bottom of the cage if he is to just barely make it around the top of cage (such that the normal force is just zero at the top) ? (Just think of it as one object with a mass of 79.2 kg going around the circle.)

Question

A daredevil  is riding a motorcycle on the inside of a spherical metal cage of radius 9.7 meters. The total mass of the person and motorcycle is 79.2 kg.  If he is to make a vertical circle within the cage at some constant speed, v, what normal force, in Newtons, does he feel at the bottom of the cage if he is to just barely make it around the top of cage (such that the normal force is just zero at the top) ?  (Just think of it as one object with a mass of 79.2 kg going around the circle.)
HELP ME . HELP ME . PLEASE !!!

drwls · Answer

First question: 2 M g at the bottom of the cage, if going fast enough to barely be in contact at the top. Second question: M V^2/R - M g = 0 Cancel the M and solve for V.