A block of mass 15 kg is placed on a long trolley . The coefficient of friction between the block and trolley is 0.18 The trolley accelerates from rest at ` 0.5 m//s^(2) ` for 20 seconds and then moves with a uniform velocity Discuss the motion of the block as viewed by (i) a stationary observer on the ground, (ii) an observer moving with the trolley.

Explanation

(a) Force experience by block , F = ma = 15 `xx` 0.5` = 7.5 N Force of friction , `F_1` = p mg = 0.18 `xx 15 xx 10 = 27 N i.e., force experienced by block will be less than the friction . So that bloxk will not move. It will remain stationary w.r.t trolley for a stationary observer on ground .
(b) The observer moving with trolley has an accelerated motion i.e. he forms non-inertial frame in which . Newton's laws of motion are not applicable . The box will be at rest relative to the observer.