Question

Five forces of the same magnitude act on a square that can rotate about point P at the midpoint of one of the edges. Rank the forces (in ascending order) acting on it according to the magnitude of the torque they create about point P

• A. $F_2,F_3,F_4,F_5,F_1$
• B. $F_3,F_4,F_1,F_2,F_5$
• C. $F_5,F_4,F_3,F_1,F_2$
• D. $F_3,F_1,F_2,F_4,F_5$

Answer 1

Answer: (D)

$F_3,F_1,F_2,F_4,F_5$

Torque will be zero for the force that act along the line of P. Hence $F_3=0$
The horizontal component of $F_1$ acts along the line of the point P, while the vertical component contributes to the torque. The vertical component of $F_1$ is $F_{1}sin\theta$ and this value will be less, since $\theta$ is nearly 180 degrees. Hence $F_1$ will produce least torque greater than zero
Amongst the options given, option d satisfies this criteria and hence is the correct option