Q 11-04-032NEETJEE MainEasy
The momentum of a particle varies with time as $\vec{p} = (4t^2\,\hat{i} - 3t^2\,\hat{j})$ kg m/s. The magnitude of the force on it at $t = 2$ s is
Answer: (A) $20$ N
Concept. $\vec F = \dfrac{d\vec p}{dt}$.
Step 1. Differentiate. $\vec F = 8t\hat i - 6t\hat j$, $|\vec F| = 10t$.
Step 2. At 2 s. $20$ N.
Answer. $20$ N (Option A).
Solution by Sreeraj P, M.Sc Physics