Q 11-07-015NEETJEE MainEAMCET 2012 (Engineering)Medium
The gravitational field in a region is given by $\vec{E} = (5\hat{i} + 12\hat{j})$ N/kg. If a particle of mass $2$ kg is moved from the origin to the point $(12\ \text{m}, 5\ \text{m})$ in this region, the change in the gravitational potential energy is
Answer: (A) $-240$ J
The field does work $W = m\vec{E}\cdot\vec{s}$, and $\Delta U = -W$:
$$\vec{E}\cdot\vec{s} = 5(12) + 12(5) = 120\ \text{J/kg}$$
$$\Delta U = -2 \times 120 = -240\ \text{J}$$
Solution by Sreeraj P, M.Sc Physics