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Question
Give one example each in which a force does (a) positive work (b) negative work, and (c) zero work.
Solution
The examples of positive, negative and zero work are as follows:
(a) Positive work - When we kick a football, it moves in the direction of the force applied and hence, the work done in this case is positive.
(b) Negative work - Work done by the frictional force on a rolling football to decrease its motion is an example of negative work, as the direction of frictional force (acting on the ball) is opposite to the direction of the football’s motion
(c) Zero work - Work done by the earth on a satellite moving around the earth is zero as the direction of the motion of the satellite is always perpendicular to the direction of the gravitational force.
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