Q 11-04-036NEETJEE MainTop questionMedium
A $10$ kg block rests on a horizontal floor. The coefficients of static and kinetic friction are $0.5$ and $0.4$. A horizontal push of $30$ N is applied. The frictional force on the block is ($g = 10\ \text{m/s}^2$)
Answer: (A) $30$ N
Limiting static friction $= \mu_s mg = 0.5 \times 100 = 50$ N.
The push ($30$ N) is less than this, so the block stays at rest and static friction adjusts to balance the push exactly: $f = 30$ N.
(Friction is $\mu N$ only at the point of slipping or while sliding.)
Solution by Sreeraj P, M.Sc Physics