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A small block with mass 0.0350 kg slides in a vertical circle of radius 0.400 m

ID: 1600507 • Letter: A

Question

A small block with mass 0.0350 kg slides in a vertical circle of radius 0.400 m on the inside of a circular track. During one of the revolutions of the block, when the block is at the bottom of its path, point A , the magnitude of the normal force exerted on the block by the track has magnitude 4.00 N . In this same revolution, when the block reaches the top of its path, point B , the magnitude of the normal force exerted on the block has magnitude 0.670 N .

How much work was done on the block by friction during the motion of the block from point A to point B ?

Explanation / Answer

normal reaction at bottom

N = mg + mu^2/R

NR = mgR +mu^2

NR/2 = mgR/2 + initial kinetic energy

initial kinetic energy = 0.7314 J

normal reaction at bottom

N = mV^2/R + mg

NR/2 - mgR/2 = final kinetic energy

final kinetic energy = 0.0654 J

work done by friction = change in mechanical energy

Wf = change in kinetic energy + change in potential energy

Wf = -0.3916J

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