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Question
Give example of a situation in which an applied force does not result in a change in kinetic energy.
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Solution
Assume a ball is tied to a string and is moving in a vertical circle. Work done by tension force will be zero and hence tension force will not cause any change in KE of the ball. Because at any instant of time the displacement is tangential and the force is central in nature, i.e., the tension in the string and the small displacement at any instant are perpendicular to each other.
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