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# CBSE Class 9 Physics Notes for Chapter 3 Gravitation

All objects in the world attract each other. This force of attraction is called gravitational force.

The formula for gravitational force experienced by two bodies is:

F= G (M x m)/d^2

FREE FALL

The acceleration during a free fall due to the gravitational force of the earth is called acceleration due to gravity. It is denoted using ‘g’. Its value is taken to be 9.8 m s-2.

The force of gravity decreases with altitude. It also varies on the surface of the earth i.e. it decreases from poles to the equator.

WEIGHT

The weight of a body is the force with which the earth attracts it which is equal to the product of the mass and the acceleration due to gravity.

FLUIDS

When a body is immersed in a liquid, it experiences buoyancy. If an object has less density than that of the liquid, it floats on the surface of the liquid. However, if the object is denser than the liquid, it sinks.