JEE Main Physics question
A block of mass 5 kg is resting on a smooth surface. At what angle a force of 20 N be acted on the body so that it acquires a kinetic energy of 40 J after moving 4 m?
Answer: (C)
Solution
Work-energy theorem: F cosθ × s = ΔKE ⟹ 20 × cosθ × 4 = 40 ⟹ cosθ = 1/2 ⟹ θ = 60°.