In the figure below, a small block of mass m = 0.034 kg can slide along the frictionless loop-the-loop, with loop radius 8 cm. The block is released from rest at point P, at height h = 7R above the bottom of the loop. (For all parts, answer using g for the acceleration due to gravity, and R and m as appropriate.)
(a) How much work does the gravitational force do on the block as the block travels from point P to point Q?
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(b) How much work does the gravitational force do on the block as the block travels from point P to the top of the loop?
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(c) If the gravitational potential energy of the block-Earth system is taken to be zero at the bottom of the loop, what is the potential energy when the block is at point P?
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(d) What is the potential energy when the block is at point Q?
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(e) What is the potential energy when the block is at the top of the loop?
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(f) If, instead of being released, the block is given some initial speed downward along the track, do the answers to (a) through (e) increase, decrease, or remain the same?
increase
decrease
remain the same