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

Explanation

Here , ` m = 15 kg , mu = 0.18 , a = 0.5 ms^(-2) , t = 20 s `
Force on the block due to motion of the trooly ` F = ma = 15 xx 0.5 = 7.5 N `
Is is obviously in the forward driction (of motion of the trolly)
Force of limitting friction on the block ` = F = mu R = mu mg = 0.18 xx 15 xx 9.8 = 26 . 46 N `
This opposes the motion of the block The block shall not move The force of stice friction F will adjust itsself equal and opposite to F the applied force
Hence a stationary observer on the ground the block will appear to be at rest relative to the trolly When trolly moves with unifrom velocity forward force is zero force is zero friction alone is acting on the block
(b) An observer moving with the trolly has accelerated motion The observer is theregfore non - inertical The law of inertia is no longer valid .