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Question
A block A, whose weight is 100 N, is pulled up a slope of length 5 m by means of a constant force F (= 100 N) as illustrated in the following figure.
- What is the work done by force F in moving block A, 5 m along the slope?
- What is the increase in potential energy of the block A?
- Account for the difference in work done by the force and the increase in potential energy of the block.
Solution
F = 100 N; S = 5 m
(a) Work done by the force F
W = F × S
= 100 × 5 = 500 J
(b) Increase in PE = mgh
= 100 × 3 = 300 J
(c) Difference in work = 500 – 300 = 200 J
This energy is used to work against the frictional force between the block and the slope of the plane, and it appears as heat.
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