A roller-coaster car has a mass 50.0 kg. The car is released from rest at a height 45.0 m above the ground and the car encounters a loop of radius 15.0 m at ground level. The initial height 45.0 m is great enough so that the car never loses contact with the track
Find the kinetic energy K of the car at the top of the loop.
Find the minimum initial height h min at which the car can be released that still allows the car to stay in contact with the track at the top of the loop.