A man draws out water from a well by pulling a rope attached to a bucket passing over a pulley. He then releases the bucket into the well after taking out the water from the bucket.
(1) Identify the forces acting on the bucket in the opposite directions.
(2) Which force is doing negative work in the first case?
(3) Which force is doing positive work in second case?
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ANSWER:
Work done by the person is the change in potential energy of the bucket and the rope.
Given, the rope has a uniform mass m. So the center of mass for the rope is at half of the length of the rope.
So, it will be at a distance h/2 from the bottom.
Work done = Change in PE of bucket+Change in PE of rope
W=Mgh+mg
2
h
=(M+
2
m
)gh
Option A.
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