JEE Main Physics question
A body of mass 3 kg is under a force, which causes a displacement in it given by S = t³/3 (in m). Find the work done by the force in the first 2 seconds.
Answer: (D)
Solution
a = d²S/dt² = 2t m/s². W = ∫F·dS = ∫₀² ma·(dS/dt)dt = ∫₀² 3(2t)(t²)dt = ∫₀² 6t³ dt = 6[t⁴/4]₀² = (3/2)(16) = 24 J.