Question

A: Torque on a body can be zero even if there is a net force on it. R: Torque and force on a body are always perpendicular.

A: A couple does not exert a net force even though it exerts a torque. R: Couple is a pair of two forces with equal magnitude but opposite directions acting simultaneously on a body in different lines of action.

A: To unscrew a rusted nut, we need a pipe wrench of longer arm. R: Wrench with longer arm reduces the force applied on arm.

(i) Why do we prefer to use a wrench, having a long arm? (ii) Under what condition, the torque due applied can be considered to be zero?