Question

In some cases, we deliberately increase friction. Explain why? (2)
Q. When the two surfaces are pressed harder, friction increases. Explain why? (2)
Q. How does the friction depend on the nature of the surface? 12)​

Answer 1

1) We deliberately increase friction by using brake pads in the brake system of bicycles and automobiles. When we are riding a bicycle, the brake pads do not touch the wheels. But when we press the brake lever, these pads arrest the motion of the rim due to friction.

2) Since the friction is due to the interlocking of irregularities in the two surfaces which slide with respect to each other, it increases when the two surfaces are pressed harder.

3) Friction depends on the nature of surfaces in contact. For a given pair of surfaces, friction depends upon the state of smoothness of those surfaces. The force of friction is greater if a rough surface is involved. Friction is caused by the irregularities on the two surfaces in contact.