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Answer :

Iqbal has to push a lighter box, so the interlocking between the surface of the lighter box and the surface of the floor is comparatively less than that of the heavier box. Because lighter box has less mass, so its' surface's roughness gets less pressed into the surface's roughness of the floor, thus making the interlocking less stronger and easier to overcome the friction using an external force of push.

While Seema has to push a similar heavier box, so the interlocking between the surface of the heavier box and the surface of the floor is comparatively more than that of the lighter box. Because heavier box has more mass, so its' surface's roughness gets more pressed into the surface's roughness of the floor, thus making the interlocking more stronger and harder to overcome the friction using an external force of push.

So Seema will have to apply a larger force.

- 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.8 Explain why sliding friction is less than static friction.
- 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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