Page 121 - Viva ICSE Science 4 : E-book

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Friction as a Force

Friction is a force that opposes motion. It is a KEY CONCEPTS

type of force that is exerted by the surface when
• Uses of friction in our daily life
an object moves across it. When two things rub
• Harmful eff ects of friction
against each other, they cause friction. The force
• How to prevent friction?
of friction always acts in the direction opposite to
the direction of the moving object. Therefore, this
force either slows down or completely stops the push

object from moving.

Friction develops between the object and the
surface when they touch or rub against each other.

For example, when we walk on the road, friction
develops between our feet and the ground as they
friction
touch each other. It is because of friction only that

we are able to walk normally, otherwise we will keep slipping off the ground. Friction is
also important because an object would never stop from moving if there is no friction.
But if there is too much friction between the object and the surface, then the object will

never move.

• Friction can occur in any medium whether solid, liquid or gas. But the amount
of friction diff ers according to the medium. A solid has more friction than liquid.
Therefore, an ice cube will slide more easily than a coin on a hard surface. It is diffi cult

to walk on wet fl oor in comparison to dry fl oor. Wet fl oor has less friction so we may
slip and fall.

• The amount of friction depends on the material from which the surface is made.
Rough surface causes more friction than smooth surface.

Let’s see what happens when we try to push a box on a carpet (rough surface) and a
wooden fl oor. When we push the box across these two surfaces, it would be harder
for us to move the box on the carpet than the wooden fl oor as there is more friction

between the carpet and the box.

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