Question

The width of a door is $40\text{cm}$. If it is released by exerting a force of $20\text{N}$ perpendicularly at its edge (away from the hinges). Compute the magnitude of torque produced which causes the door to open.

• A. $10\text{Nm}$
• B. $0\text{Nm}$
• C. $8\text{Nm}$
• D. $6\text{Nm}$

Answer 1

The correct option is C $8\text{Nm}$

Force applied $F=20\text{N}$
Distance of application of force from the hinge i.e. distance amid the line of action of force and axis of rotation is
$d=40\text{cm}=0.40\text{m}$
Thus, we have
Torque, $\tau =Fd\sin {90}^{\circ }$ (As force acting perpendicularly)
$\Rightarrow \tau =0.40\times 20=8\text{Nm}$