1.

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:

Answer»

1 Joule
10 J
100 J
1000 J

Solution :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


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