Question

A rod $OA$ of mass $4kg$ is held in horizontal position by a massless string $AB$ as shown in figure. Length of the rod is $2m$. Find
(a) tension in the string.
(b) net force exerted by hinge on the rod. $(g=10m/s^2)$.

Answer 1

For equilibrium condition
$F_y+T\sin {60}^{\circ }=mg...\left(i\right)$
$F_x=T\cos {60}^{\circ }...\left(ii\right)$
Torque about point $A$
$mg\frac{l}{2}=F_y\times l$
$F_y=\frac{mg}{2}=\frac{9\times 10}{2}$
$=20N$