Question

A rod of length 1.0 m and mass 0.5 kg fixed at one end is initially hanging, vertical. The other end is now raised until it makes an angle ${60}^{\circ }$ with the vertical. How much work is required?

• A. $1.225J$
• B. $2.225J$
• C. $2.45J$
• D. $4.45J$

Answer 1

The correct option is A $1.225J$

For increase in gravitational potential energy of a rod we see the centre of the rod.
W=change in potential energy

$=mg\frac{l}{2}(1-\cos \theta )$

Substituting the values, we have

$W=\left(0.5\right)\left(9.8\right)\left(\frac{1.0}{2}\right)(1-\cos {60}^{\circ })$

$=1.225J$