Q 11-04-047NEETJEE MainMedium
A box lies on the floor of a truck. The coefficient of kinetic friction between them is $0.3$. The truck accelerates at $5\ \text{m/s}^2$, which is enough to make the box slide. The acceleration of the box relative to the truck is ($g = 10\ \text{m/s}^2$)
Answer: (D) $2\ \text{m/s}^2$ towards the rear
Concept. Kinetic friction gives the box $\mu_kg$ forward (ground frame).
Step 1. Box. $3\ \text{m/s}^2$; truck $5\ \text{m/s}^2$.
Step 2. Relative. $3 - 5 = -2$: $2\ \text{m/s}^2$ towards the rear.
Answer. $2\ \text{m/s}^2$ towards the rear (Option D).
Solution by Sreeraj P, M.Sc Physics