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 will acquired a kinetic energy of 40J after moving 4m 

(A) 30° 

(B) 45° 

(C) 60° 

(D) 120°

Answer 1

Correct option: (C) 60°

Explanation:

m = 5 kg

F = 20N 

KE = 40 J, s = 4 m 

Δ K = F ∙ S cos θ 

40 = 20 × 4 × cos θ 

cos θ = (1/2) 

θ = 60°