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Answer :

Friction comes into play when irregularities or the minute roughness present in the surfaces of two objects, get interlocked upon coming in contact with each other.

In sliding friction, the time given for interlocking is very small and thus the resulting interlocking is not so strong. Therefore with the application of less external force, one can overcome this type interlocking.

While in case of static friction, the interlocking between the two surfaces of the two objects is much stronger as compared to that of sliding friction. So this type of interlocking requires more external force to overcome the friction created because of that interlocking. Hence, sliding friction is less effective than static friction.

- Q.1 Fill in the blanks. (a) Friction opposes the ______ between the surfaces in contact with each other. (b) Friction depends on the ______ of surfaces. (c) Friction produces ______ (d) The sprinkling of powder on the carrom board _______ friction. (e) Sliding friction is _______ than the static friction.
- Q.2 Four children were asked to arrange forces due to rolling, static and sliding frictions in a decreasing order. Their arrangements are given below. Choose the correct arrangement. (a) rolling, static, sliding (b) rolling, sliding, static (c) static, sliding, rolling (d) sliding, static, rolling
- Q.3 Alida runs her toy car on a 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 (a) wet marble floor, dry marble floor, newspaper and towel. (b) newspaper, towel, dry marble floor, wet marble floor. (c) towel, newspaper, dry marble floor, wet marble floor. (d) wet marble floor, dry marble floor, towel, newspaper.
- Q.4 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.
- Q.5 You spill a bucket of soapy water on a marble floor accidentally. Would it make it easier or more difficult for you to walk on the floor? Why?
- Q.6 Explain why sportsmen use shoes with spikes.
- Q.7 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?
- Q.9 Give examples to show that friction is both a friend and a foe.
- Q.10 Explain why objects moving in fluids must have special shapes.

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