Question

Two blocks $A$ and $B$ are placed one over the other on a smooth horizontal surface. The maximum horizontal force that can be applied on the upper block $B$, so that $A$ and $B$ move without separation is $49N$. The coefficient of friction between $A$ and $B$ is:

• A. $0.2$
• B. $0.3$
• C. $0.5$
• D. $0.8$

Answer 1

The correct option is C $0.5$

Given, $F=49N,M_A=7kg,M_B=3kg,\mu =?$
Equation of motion of two blocks-system
$F_{max}=\mu (M_A+M_B)\cdot g$
$\mu =\frac{F}{(M_A+M_B)\cdot g}$
$=\frac{49}{(7+3)\cdot 9\cdot 8}$
$=\frac{49}{10\times 98}$
$=0.5$.