Page 123 - Viva ICSE Science 4 : E-book

• It produces heat. This can be observed when we rub our hands
together quickly. This makes our hands warmer.

• Heat produced by lamp or electric stove is because of friction.

• Friction produces sound. For example, friction between

the violin string and its bow produces sound.

• The friction between the pencil tip and the paper helps
us to write. We hold the pencil because of friction. Writing

is possible due to friction between lead and paper. We
cannot write on a butter paper as it is smooth and has
less friction. Similarly, we can rub out with an eraser due

to friction.

TIME TO REVISE

What will happen
1. to a moving object if there is no friction.

2. to an object if there is excess friction.

Harmful Eff ects of Friction

Friction is useful but too much friction can cause problems as well. Some of the problems
that are caused due to excess friction are the following.

• Excess friction can make it diffi cult for us to slide a heavy box across the fl oor, or ride

a bicycle on the road.
• Friction causes wear and tear of machine parts that constantly rub against each

other.

• It gives rise to unwanted heat, due to which the useful energy gets wasted as heat
energy. Sometimes, even fi re accidents can take place in the vehicles due to excess
frictional force.

• It acts all the time and slows down the speed of a moving object. For this, extra force

has to be applied from time to time to keep the objects moving. This causes the
wastage of fuel and energy.

• It produces noise in machines. For example, if a running fan makes squeaking sound,
it is because of friction.

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