Page 66 - Innovator's Science-8

Activity-8 Aim: To measure the force of fric on
Materials Required: A spring balance, a shoe box with shoes, strong thread and
Experiential Learning
table.
Procedure: Place the shoes box with the shoes inside it on
the tabletop. Wrap and e a thread around it as shown in
the figure. connect the hook of the spring balance to the
thread and pull the box slowly, increasing the force un l
the box begins to slide.

Now, put two round pencils below the box and pull it again.
Note down the reading on the scale of spring balance.
Make sure that the spring balance is parallel to the surface on which the box is kept.

We can therefore define friction as a force that slows down moving
objects or prevents stationary objects from moving. The frictional force

between two surfaces depends on shape, texture and mass of the
objects in contact.

Science Archimedes' Principle
Bytes
A famous Greek scientist, Archimedes, discovered that when a body is
Testimony fully or partially immersed in a liquid, it experiences an upward force
There are some rocks that
can float on water. One equal to the weight of the liquid displaced by it. This is known as
such rock is pumice, Archimedes' Principle. If the weight of the displaced liquid is less than
formed during volcanic the weight of the object, the object sinks. If both are equal, the object
erup ons. It contains
many trapped air bubbles floats.
that make it lighter than This principle is used in designing ships and submarines, which float on
water.
water despite being made of heavy metal.

State whether the following statements are true or false. Correct the false
Run Through
statements.
Intellectual Development 1. Force can be applied to an object only by touching the object. ________
2. Frictional force is a contact force. ________
3. Charges are of two types, positive and negative. ________
4. The poles of a bar magnet always attract each other. ________
5. Force of friction always acts in the direction of motion. ________

Know Your Scientist
Isaac Newton (1643-1727) was an English scientist and mathematician who made groundbreaking
discoveries in physics. He explained the laws of motion and the universal law of gravitation, showing that every
object in the universe attracts every other object. His studies on force and motion form the foundation of
modern physics. Newton also developed the reflecting telescope and studied light and colour. His work on
forces continues to help us understand how objects move, fall, and interact on Earth and in space.

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Science-8