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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.)
Answer
If 2 people push
Then car moves with uniform velocity
So, Acceleration = 0
That means
Total Force on Body is balanced
Therefore,
Force by 2 People = Force of Friction
2F = Force of Friction
Force of Friction = 2F
If 3 people push
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Then car moves with Acceleration = 0.02 m/s2
Net Force = Force of 3 people – Force of Friction
= 3F – 2F
= F
So, let’s find F
Given
Mass of motor car = m = 1200 kg
Acceleration = a = 0.2 m/s2
Force = F
Now
Force = Mass × Acceleration
F = 1200 × 0.2
F = 1200 × 2/10
F = 120 × 2
F = 240N
Thus, each person pushes the motorcar by 240 force
