Arrange the frictional force acting on different surfaces in increasing order:

You allow a glass ball to move on cemented floor, marble, water, towel and ice.

• cemented floor, water, towel, marble, ice

• marble, cemented floor, water, ice, towel

• ice, water, marble, towel, cemented floor

• water, ice, marble, cemented floor, towel

Suppose your writing desk is tilted a little. A book kept on it starts sliding down. Show the direction of frictional force acting on it.

You spill a bucket of soapy water on a marble floor accidently. Would it make easier or more difficult for you to walk on the floor? Why?

Explain why sportsmen use shoes with spikes.

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

Explain why sliding friction is less than static friction.

Give examples to show that friction is both a friend and a foe.

Explain why objects moving in fluids must have special shapes.

What is force of friction?

What is the cause of friction between two surfaces?

Which is small sliding friction or static friction?