Q 12-04-152JEE MainJEE Main 2022 (26 Jul, Shift 1)Easy
A charged particle is moving in a uniform magnetic field $(2\hat i + 3\hat j)\ \text{T}$. If it has an acceleration of $(\alpha\hat i - 4\hat j)\ \text{m s}^{-2}$, then the value of $\alpha$ will be
Answer: (B) 6
The magnetic force, and hence the acceleration, is perpendicular to $\vec B$:
$$(\alpha\hat i - 4\hat j)\cdot(2\hat i + 3\hat j) = 2\alpha - 12 = 0\ \Rightarrow\ \alpha = 6$$
Solution by Sreeraj P, M.Sc Physics