Question

If a uniform beam of $1m$ is balanced as shown above, what would be the moment of force F about point W?

• A. $110Ncm$
• B. $40Ncm$
• C. $220Ncm$
• D. $80Ncm$

Answer 1

The correct option is C $220Ncm$

If the uniform beam is in rotational equilibrium, net torque on the beam about point U must be zero i.e. ${\tau }_U=0$

Consider anti-clockwise direction to be positive.

$\therefore$ ${\tau }_U=-\left(F\right)\left(40\right)+\left(3\right)\left(10\right)+\left(2\right)\left(40\right)=0$

$⟹F=2.75N$

Torque of $F$ about W, $\tau =F\times 80=2.75\times 80=220Ncm$