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 s2. With what force does each person push the motorcar? (Assume that all persons push the motorcar with the same muscular effort.)
Here, mass of motorcar, m = 1200 kg Let each person exerts a force F on the motorcar. Total force of two persons = F + F = 2 F As this force gives a uniform velocity to the motor car along a level road, it must be a measure of the force of friction (ƒ) between the motorcar and the road, i.e., ƒ= 2F. When three person push, total force applied = F + F + F = 3F Force that produces acceleration (a = 0.2 m s-2), i. e., ma = 3F – f = 3F – 2F = F or F = ma = 1200 × 0.2 = 240 N