Question

A meter stick of mass 400 g is pivoted at one end and displaced through an angle ${60}^0$. The increase in its potential energy is

Answer 1

Here

Mass of stick ,$m=0.4kg$

Length of stick , $l=1m$

Initial Potential energy $=\frac{mgl}{2}=\frac{0.4\times 10\times 1}{2}=2J$

At ${60}^0$ angle ,

Final Potential energy $=\frac{mgl(1-cos{60}^0)}{2}=\frac{0.4\times 10\times 1(1-0.5)}{2}=1J$.

So , Its potential energy decreased by $2-1=1J$