Q. A door 1.6 m wide requires a force of 1 N to be applied at the free end to open or close it. The force that is required at a point 0.4 m distance from the hinges for opening or closing the door is
A) 1.2 N
B) 3.6 N
C) 2.4 N
D) 4 N
Explanation
(d) Here, torque $\tau = 1.6 \times 1 = 1.6$ Nm
So, when $d = 0.4$ m,
$F = \frac{\tau}{d} = \frac{1.6}{0.4} = 4$ N
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.