Torque of a Couple

Steps:

• A couple consists of two equal and opposite forces separated by perpendicular distance d.
• Torque due to a single force is F times perpendicular distance from pivot.
• For a couple, total torque is sum of torques from both forces, each contributing F * d.
• Thus, net torque equals F * d, independent of pivot point.

Why C is correct:

• By definition, the torque of a couple is F times the perpendicular distance d between the forces.

Why the others are wrong:

• A: Incorrectly halves the torque, ignoring full contribution from both forces.
• B: Inverts the relationship, confusing torque with something like pressure.
• D: Doubles the torque, mistakenly adding extra factor beyond F * d.

Final answer: C