Question

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?

(a) What are the differences between the centre of gravity and the centre of mass? (b) A square plate of mass 120 g and edge 5.0 cm rotates about one of edges. If it has a uniform angular acceleration of 0.2rad/s², what torque acts on the plate?