Q 11-04-046JEE MainTop questionHard
A $2$ kg block rests on an $8$ kg block, which lies on a smooth floor. The coefficient of static friction between the blocks is $0.3$. The maximum horizontal force that can be applied to the lower block so that the two move together is ($g = 10\ \text{m/s}^2$)
Answer: (C) $30$ N
The top block is accelerated only by friction, so its maximum acceleration is $\mu_s g = 3\ \text{m/s}^2$.
For both to move together with this acceleration:
$$F_{max} = (2 + 8) \times 3 = 30\ \text{N}$$
Solution by Sreeraj P, M.Sc Physics