Question

A rod PQ of mass M and length L is hinged at end P. The rod is kept horizontal by a massless string tied to point Q as shown in figure. When string is cut, the initial angular acceleration of the rod is:

• A. $ \frac{2g}{3L}$
• B. $ \frac{3g}{2L}$
• C. \(\frac gL\)
• D. \(\frac  {2g} {L}\)

Answer 1

The Correct Option is B

\(\tau = I \alpha \)
\(\Rightarrow mg \left( \frac{L}{2} \right) = \left( \frac{ml^2}{3} \right) \alpha\)
\(\Rightarrow \alpha = \frac{3g}{2L}\)

So, the correct option is (B): \(\frac{3g}{2L}\)