A roller-coaster car may be represented by a block of mass 50. The car is released from rest at a height = 54.0 above the ground and slides along a...

A roller-coaster car may be represented by a block of mass 50.0 . The car is released from rest at a height = 54.0 above the ground and slides along a frictionless track. The car encounters a loop of radius = 18.0 at ground level, as shown. As you will learn in the course of this problem, the initial height 54.0 is great enough so that the car never loses contact with the track.