A metre stick of mass 400 gm is pivoted at one end and displaced through an angle of 60°. The increase in its P.E. is:

Options

A. 1 Joule
B. 10 J
C. 100 J
D. 1000 J

Answer

a

Explanation

Here mass of metre rod is concentrated at the centre of metre rod when the rod.Is displaced through `60^(@)` then centre of mass is raised through height h.
`cos 60^(@)=(OD)/(OC)=(1/2-h)/(1/2)`
`:.1/2=(1/2-h)/(1/2)implies1/2-h=1/4impliesh=(1)/(4m)`
`:.` Increases in potential energy=mgh=`0.4xx10xx1/4`
=1 J