Question

Iqbal has to push a lighter box and Seema has to push same heavier box. Who will have to apply larger force and why?

Answer 1

Seema will have to apply a larger force.

Force of friction arises because of interlocking of irregularities on the two surfaces in contact. When a heavy object is placed on the floor, the interlocking of irregularities on the surfaces of box and floor becomes strong. This is because the two surfaces in contact are pressed harder. Hence, more force is required to overcome the interlocking. Thus, to push the heavier box, Seema has to apply a greater force than Iqbal.

Or we can simply explain as the force of friction is increased if the two surfaces are pressed harder. A heavier box will apply more pressure on the floor and hence Seema will experience more frictional force