Question

In the pulley system shown in the figure, the radii of the bigger and smaller pulleys are $2\text{m}$ and $1\text{m}$ respectively. Find the resultant torque at point $\text{O}$. (Take $g=10{\text{m/s}}^2)$

• A. $200\text{N-m}$
• B. $100\text{N-m}$
• C. $0\text{N-m}$
• D. $50\text{N-m}$

Answer 1

The correct option is C $0\text{N-m}$

As we know,
Torque $=r_{\perp }F$
Torque on smaller pulley $=r_{\perp }\left(mg\right)$
$=1\times (10\times 10)=100\text{N-m}$ (clockwise)
Torque on bigger pulley $=r_{\perp }\left(mg\right)$
$=2\times (5\times 10)=100\text{N-m}$ (anticlockwise)
Net torque on point $\text{O}={\tau }_1+{\tau }_2$
$=100+(-100)$
$=0\text{N-m}$