Question

Two blocks A and B of masses 10 kg and 15 kg are placed in contact with each other at rest on a rough horizontal surface as shown in the figure. The coefficient of friction between the blocks and surface is 0.2. A horizontal force of 200N is applied to block A. The acceleration of the system is
(Take g=10 $m{s}^{-2}$)

• A. 4 $m{s}^{-2}$
• B. 6 $m{s}^{-2}$
• C. 8 $m{s}^{-2}$
• D. 10 $m{s}^{-2}$

Answer 1

Answer: (B)

6 $m{s}^{-2}$

Here, mass ob block A, $m_A=10kg$

Mass of block B,$m_B=15kg$

Coefficient of friction between and the blocks and surface, $\mu =0.2$

Applied force = 200 N

Froce of friction on A =$\mu N_A=\mu m_{A}g=0.2\times 10\times 10=20N$

Force of friction on B =$\mu N_B=\mu m_{B}g==0.2\times 15\times 10=30N$

Taking two blocks forming one system, therefore net force acting on the blocks is

F=200-20-30=150 N

Let a be common acceleration of the system.

$\therefore a=\frac{F}{m_A+m_B}=\frac{150N}{(10+15)kg}=6m{s}^{-2}$