Question

A block $A$ of mass $100kg$ rests on another block $B$ of mass $200kg$ and is tied to a wall as shown in the figure. The coefficient of friction between $A$ and $B$ is $0.2$ and that between $B$ and the ground is $0.3$ . The minimum force $F$ required to move the block $B$ is $(g=10m{s}^{-2})$

• A. 900 N
• B. 200 N
• C. 1100 N
• D. 700 N

Answer 1

Answer: (C)

Friction force between block $A$ and block $B$ and between block $B$ and surface will oppose the $F$
$\therefore F=F_{AB}+F_{BS}$
$={\mu }_{AB}{m}_{A}g+{\mu }_{BS}\left(m_A+m_B\right)g$
$=0.2\times 100\times 10+0.3(100+200)10$
$=200+900=1100N$
This is the required minimum force to move the block $B$.