Question

frictions also depend in the shape of object explain

Answer 1

You might have seen a driver of a car or a truck slowing down the vehicle at a traffic signal. You, too, slow down your bicycle whenever needed by applying brakes. Have you ever thought why a vehicle slows down when brakes are applied? Not only vehicles, any object, moving over the surface of another object slows down when no external force is applied on it. Finally it stops. Have you not seen a moving ball on the ground stopping after some time? Why do we slip when we step on a banana peel (Fig.1)? Why is it difficult to walk on a smooth and wet floor?

Fig.1 A boy falls down when he steps on a banana peel

You will find the answers to such questions in this chapter.

12.1 Force of Friction

Activity 1

Gently push a book on a table [Fig.2(a)]. You observe that it stops after moving for some distance. Repeat this activity pushing the book from the opposite direction [Fig.2(b)]. Does the book stop this time, too? Can you think of an explanation? Can we say that a force must be acting on the book opposing its motion? This force is called the force of friction.

Answer 2

friction does depend on shape of object because that influences the point of contact of the object with the surface. For example- tyres are circular and not square because they offer less friction and obviously offer rolling motion