Question

In the figure shown ground is smooth, whereas surface between $10kg$ block and $5$ kg block is rough. A force of magnitude $30$ N is applied on $10$ kg block, horizontally. If net work done by friction on the system (on $10$ kg and $5$ kg blocks) in any time frame is zero, then coefficient of friction between $10$ kg and $5$ kg can be

• A. $0.2$
• B. $0.3$
• C. $0.4$
• D. $0.6$

Answer 1

The correct option is A $0.2$

Since there is no work done by friction, there is no relative motion between the blocks.

Hence , for $10$ kg block,

$30f=10a$

For $5$ kg block,

$5a=f$

$30=15a$

$a=2m{s}^{-2}$

$\begin{array}{c}f=\mu mg\\ f=\frac{1}{2}\times 5\times 10\\ f=0.2\end{array}$