Page 125 - Science Class 08

Muscular force : The force applied by our muscles
Mechanical force : The force applied by a moving object on a body

Lubricating : Applying oil or grease to reduce friction
Gravitational force : Force of attraction generated by the earth
Magnetic force : Force generated by a magnet

Electrostatic force : Force generated by rubbing two objects
Pressure : Force applied in a unit area

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i Force can change the speed of a moving object, can change the direction of a moving object
and force can also change the shape of an object.
i Force can be categorised into contact force and non-contact force.
i Contact force can be categorised into muscular force, mechanical force and frictional force.
i Friction has some advantages as well as disadvantages.
i Friction can be reduced by polishing, lubricating or streamlining.

i Friction can also be increased.
i Non-contact force can be categorised into gravitational force, magnetic force and
electrostatic force.
i Force applied on a unit area is called pressure.
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i The unit of force is Newton (N) and the unit of pressure is N/m .
i Liquids exert pressure in all directions.
i The weight exerted by the vertical column of all layers of air of atmosphere on unit area of
earth’s surface is called the atmospheric pressure.

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A. Tick (3) the correct op on.
1. Force cannot:
(a) stop a moving object
(b) change the direc on of a moving object

(c) move a sta onary object
(d) dry clothes
2. Which of the following is not a contact force?
(a) Muscular force (b) Mechanical force

(c) Fric onal force (d) Gravita onal force
3. Moving wind or water creates:
(a) Mechanical force (b) Gravita onal force

(c) Muscular force (d) Electrosta c force

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