Page 144 - Active Science 5 Ebook and Activity

b. It helps in writing. You cannot move a pencil without friction with paper. An eraser
uses friction to rub off the mistakes.

c. Without friction, you cannot start a car or stop it.

Disadvantages of Friction

a. Excess friction means excess force. To move a heavy vehicle, extra fuel will be needed
to power the vehicle as in cars, boats, airplanes, etc.

b. Excess friction makes movement difficult. For example, riding a bicycle and walking

on deep snow. Soles of shoes and a pencil eraser are example of materials that wear
out because of friction.

Let’s Recapitulate

Fill in the blanks.

1. A push or pull applied to move an object is called __________________.
2. If we throw anything upwards, it always comes down because of the earth’s
_________________.

3. The opposing force between two charged particles at a distance is called __________________.
4. __________________ is the power which pulls different materials together.
5. The opposition of motion is called __________________.

E nergy
Energy is the capacity to do work. There are several forms of energy such as kinetic

energy, heat energy, potential energy, etc. Energy can never be created or removed;
it can transfer from one form to another. For example, the water we drink gives us the
energy to survive, the sun gives us the heat and light energy.

Heat Energy

Heat is a type of energy. It is obtained by burning fuels like kerosene,
petrol and coal. This energy is transmitted from one body to another
in three ways– radiation, convention or conduction. We cook food
using heat energy. Candle

Light Energy

Light is a form of energy which helps us to see
things around us. The electric bulb, candle, Tube
tubelight, lamp, etc., are the sources that Bulb

produce light. All plants use light energy to make their food.
Table Lamp

144 Active Science-5