A roller coaster car (mass = 988 kg including passengers) is about to roll down a track. The diameter of the circular loop is 20.0 m and the car starts out from rest 40.0 m above the lowest point of the track. Ignore friction and air resistance.
(a) At what speed does the car reach the top of the loop?

(b) What is the force exerted on the car by the track at the top of the loop?
(c) From what minimum height above the bottom of the loop can the car be released so that it does not lose contact with the track at the top of the loop?

40.0 m 20.0 m