Why will a sheet of paper free fall slower in air than one that is crumpled into a ball?

Sprinkling of powder on the carrom board ____________ friction.

Sliding friction is ____________ than the static friction.

Four children were asked to arrange forces due to rolling, static and sliding frictions in a decreasing order. Their arrangement are given below. Choose the correct arrangement:

Alida runs her toy car on dry marble floor, wet marble floor, newspaper and towel spread on the floor. The force of friction acting on the car on different surfaces in increasing order will be :

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.