Question

If mass of $A=10$ kg . coefficient of static friction = $0.2$, coefficient of kinetic friction $0.2$. Then mass of $B$ to start motion is

• A. 2 kg
• B. 2.2 kg
• C. 4.8 kg
• D. 200 gm

Answer 1

The correct option is A 2 kg

$ma=T-\mu \rho mg............\left(1\right)$

friction is static as we require limiting condition.

for limiting case $a=0$

So,

$\left(i\right)$ becomes, $T=mg$

$\left(ii\right)$ becomes, $T={\mu }_s\times w\times g$

comparing both:

$\begin{array}{c}m\times g=0.2\times w\times g\\ m=2kg\end{array}$

Hence, minimum mass require to initiate the motion $mg=2kg$