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Question
A boy is moving on a straight road against a frictional force of 5 N. After travelling a distance of 1.5 km he forgot the correct path at a roundabout (Fig. 11.1) of radius 100 m. However, he moves on the circular path for one and half-cycle and then he moves forward up to 2.0 km. Calculate the work done by him.
Solution
Frictional force, F = 5 N As frictional force was always there in the motion of boy,
∴ Work done by boy = Force * Total distance covered
= 5 N × [1.5 km + 32 × 2× π × 0.1 km +2 km]
= 5 N × 4.442 km
= 5 N × 4442m
= 22210J
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