Question

What is the acceleration of the block and trolly system as the fig., if the coefficient of kinetic friction between the trolly and the surface is 0.04 ? Also Calculate friction in the string. Take g = 10 m/s², mass of the string is negligible. 

Answer 1

Free body diagram of the block

30 – T = 3a       .....(i)

Free body diagram of the trolley

T – f_k = 20 a ...(ii) 

where f_k = µ_k N = 0·04 × 20 × 10 = 8 N 

Solving (i) & (ii), 

a = 0·96 m/s² and T = 27·2 N