Question

A 5 kg block is kept on a horizontal platform at rest. at time t = 0, the platform starts moving with a constant acceleration of 1 m/s². the coefficient of friction μ between the block and the platform is 0.02. The work done by the force of friction on the block in the fixed reference frame in 10 seconds is

• A. +10 J
• B. −10 J
• C. +250 J
• D. −250 J

Answer 1

Answer: (A)

+10 J

Answer 2

Limiting force of friction = μN = 0.02 (50) = 1N

∴ The block will slide on the platform.

F_f = ma = 1 ; a = $\frac { 1 } { 5 }$m/s²

∴ displacement d = work of f_f = 1n (10 m) = +10 j, hence the correct choice is (1).