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A roller-coaster car may be represented by a block of mass 50.0 kg. The car is released from rest at a height h = 48.0 m above the ground and slides along a frictionless track. The car encounters a loop of radius R = 16.0 m at ground level, as shown. As you will learn in the course of this problem, the initial height 48.0 m is great enough so that the car never loses contact with the track .

**Part A**

Find the kinetic energy
of the car at the top of the loop.

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**Express your answer numerically, in joules.**

**Part B**

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.**Express your answer numerically, in meters.**

♦ Relevant knowledge

According to the law of conservation energy, energy cannot be created or destroyed. It can only be transformed from one form to the other. A body can possess kinetic energy by virtue of its motion. We need to provide kinetic energy to a body that needs to move. A momentum exchange occurs when two bodies collide. The square root of kinetic energie is the direct measure of how much momentum there is.

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