Question

A mass of 2 kg is placed on a trolley of 20 kg sliding on a smooth surface. The coefficient of friction between the mass and surface of trolley is 0.25. A horizontal force of 2N is applied to the mass. The acceleration of the system and the frictional force between the mass and surface of trolley are

• A. 1.8 ms^-2, 0.09 N
• B. 0.9 ms^-2, 18 N
• C. 0.09 ms^-2, 1.8 N
• D. 1 ms^-2, 2 N

Answer 1

Answer: (C)

0.09 ms^-2, 1.8 N

Answer 2

Limiting frictional force = μmg

= 0.25 × 2 × 10 = 5 N

So the block and trolley will not have relative motion for a force of 2N.

Here, 2 = (20 + 2)a

or a = $\frac { 2 } { 22 } = \frac { 1 } { 11 } = 0.09 \mathrm {~ms} ^ { - 2 }$ Then frictional force = 20 × 0.09n = 1.8 N