Question

A truck is accelerating on horizontal road with an acceleration $20$ $m/s^2$. A block placed against the rear wall of the truck. It has a mass of 100kg and coefficient of friction between it and the wall is 0.8.

• A. Acceleration of the box is $20$ $m/s^2$
• B. The friction acting on the block is 1600 N
• C. The friction acting on the block is 1000 N
• D. The contact force between the wall and block is $1000\sqrt{5}$ N
• E. The contact force between the wall and block is $0$ N

Answer 1

Answer: (A), (B), (D)

The correct options are
A Acceleration of the box is $20$ $m/s^2$
B The friction acting on the block is 1600 N
D The contact force between the wall and block is $1000\sqrt{5}$ N

Since the block remains in contact with the wall and moves with the truck, the acceleration of block=Acceleration of truck=$20m/s^2$

Thus pseudo force acting due to this acceleration=Normal reaction between wall and block=$N=ma=2000newtons$

Thus friction acting on block=$\mu N=1600newtons$