Question

A meter stick of mass 400 gm is pivoted at one end and displaced through an angle 600 the increase in its P.E. is ______ J. 

(A) 2 

(B) 3 

(C) Zero 

(D) 1

Answer 1

Correct option: (D) 1

Explanation:

Centre of mass of stick is at midpoint when it is displaced by 60° Its C.M. rises up to height h  looking at figure

h = (l/2) – (l/2)cosθ

given l = 1m,

h = (1/2) – (1/2) cos 60 = (1/2) – (1/4) = (1/4)m

increase in potential energy = mgh

= 0.4 × 10 × (1/4)

= 1