Question

Two men support a uniform horizontal rod at its two ends. If one of them suddenly lets go, the force exerted by the rod on the other man will

• A. Remain unaffected
• B. Increase
• C. Decrease
• D. Become unequal to the force exerted by him on the beam.

Answer 1

The correct option is C Decrease

Before released, force exerted by the rod on each man are equal to half of the weight of the rod,

$N=\frac{w}{2}$ ......1

After the released,

Let take linear acceleration of CG is $a$ and angular acceleration is $\alpha$.

$a=\frac{l}{2}\times \alpha$ ....... 2

Taking Moments about one end where man holds the rod,

$mg\times \frac{l}{2}=\frac{m{l}^2}{3}\alpha$

$\Rightarrow \alpha =\frac{3g}{2l}$ .......3

Let reaction faced by man is N

$\therefore mg-N=ma$ ....... 4

Using equations 2 and 3 in equation 4,

$N=\frac{mg}{4}=\frac{w}{4}$ ....... 5

Comparing equation 1 and 5 we find that force exerted by the rod is decreased.