Gravitation
1. According
to the law of gravitation the force of attraction between any two objects is
proportional to the product of their masses and inversely proportional to the
square of the distance between them. The law applies to objects anywhere in the
universe. Such a law is said to be universal.
2.
Universal gravitational
constant G = 6.673×10-11
Nm2kg-2
3. Gravitation
is a weak force unless large masses are involved.
4.
Acceleration with which a
body falls towards the centre of the earth is called acceleration due to
gravity (g).
5. The
force of gravity decreases with altitude. It also varies on the surface of the
earth, decreasing from poles to the equator.
6. Mass
is the quantity of matter contained in the body.
7. Weight
of the body is the force with which the earth attracts the body.
8. The
weight is equal to the product of mass and acceleration due to gravity.
9. Mass
of a body does not change but weight of a body is different at different
places.
10. The force
acting on a body perpendicular to its surface is called thrust.
11. The force
acting per unit area of the object is known as pressure.
12. The upward
force exerted by a liquid when a body is immersed in the liquid is called up
thrust or buoyant force.
