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Question
Two persons manage to push a motorcar of mass 1200 kg at a uniform velocity along a level road. The same motorcar can be pushed by three persons to produce an acceleration of 0.2 m s−2. With what force does each person push the motorcar? (Assume that all persons push the motorcar with the same muscular effort.)
Solution
Here, mass of the Motorcar, m = 1200 kg
Let each person exert a force F on the motorcar.
Total force of two persons = F + F = 2 F
As this force gives the motorcar a uniform velocity along a level road, it must be a measure of the force of friction (f) between the motorcar and the road, i.e., f = 2F.
When three person push, total force applied = F + F + F = 3 F
Force that produces acceleration (a = 0.2 ms-2),
i.e., ma = 3 F - f
= 3F - 2F
= F
or F = ma
= 1200 × 0.2
= 240 N
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