Question

Find the minimum value of coefficient of friction between the $4\text{kg}$ block and the surface for the system to be at rest for the figure shown, (Block $A=4\text{kg}$ and block $B=3\text{kg}$)

• A. $0.4$
• B. $0.5$
• C. $0.6$
• D. $0.75$

Answer 1

The correct option is D $0.75$

By FBD of the blocks


For the system to be in rest, $a=0$
So, $T=3g$
From FBD of 4kg block
$f=T$, where $f=\mu N$ is the frictional force on the block
On equating both the equation
$4\mu g=3g$
$\mu =\frac{3}{4}=0.75$