Question

Prove that friction depends on the nature of two surfaces in contact

Answer 1

No surfaces on earth are perfectly smooth.All have tiny bumps and holes. So when one body moves over another body these bumps and holes get in each other's way producing friction.Smoother is a surface lesser is the holes and bumps and so lesser is the frictional force.Take a ball .Roll it over a tiled floor first

Then cover the floor with a carpet.Roll the ball over the carpet.It will be seen that the ball rolls faster on the tiled floor

than on the carpeted floor because the

marble floor is smoother than the carpeted floor and so the friction is less

acting on the ball when it rolls over the tiled floor.And lower the frictional force

more is the speed of a moving body.

Again try writing on a glass slide first and then on paper with a pencil. When we write with a pencil ,the friction generated

between the paper and the tip of the pencil makes tiny particles of carbon ruboff and leave a mark on the paper.

When we write over glass slide due to the smooth surface of the glass the friction generated is low so the carbon

particles are not rubbed off from the tip

so we can't write but since paper has a

relatively more rough surface the frictional force is higher so the carbon particles are rubbed off from the tip of the pencil and we can write