Page 1 - Demo

FRICTIONYou might have seen a driver of acar or a truck slowing down thevehicle at a traffic signal. You, too,slow down your bicycle wheneverneeded by applying brakes. Have youever thought why a vehicle slowsdown when brakes are applied? Notonly vehicles, any object, moving overthe surface of another object slowsdown when no external force isapplied on it. Finally it stops. Haveyou not seen a moving ball on theground stopping after some time?Why do we slip when we step on abanana peel (Fig. 12.1)? Why is itdifficult to walk on a smooth and wetfloor?Fig. 12.1 : A boy falls down when he steps on abanana peel12.1 Force of FrictionActivity 12.1Gently push a book on a table [Fig.12.2(a)]. You observe that it stopsafter moving for some distance.Repeat this activity pushing thebook from the opposite direction[Fig. 12.2, (b)]. Does the book stopthis time, too? Can you think of anexplanation? Can we say that a forcemust be acting on the bookopposing its motion? This force iscalled the force of friction.Fig. 12.2 (a), (b) : Friction opposes relative motionbetween the surfaces of thebook and the table(a)(b)You will find the answers to suchquestions in this chapter.%u00a9 NCERTnot to be republished