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Force of Gravity
What
is the force of gravity?
Why is it that things generally fall to the ground if not supported? Why
is it that when we throw thing up into the sky, they always drop back
to the ground?
Newton discovered that there is a small attractive force between any two
bodies. Usually this force is so small that it is impossible for us to
feel.
However, if one of the bodies is the earth, the force may be very great.
Wherever we are on Earth, a strong force pulls us towards the centre of
it.
We call this the force of gravity.
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What
is weight? How is it measured?
Weight is a force. The weight of an object is the force of gravity pulling
it towards the Earth.
The greater the force of gravity action on an object, the more it weighs.
The weight of an object is measured in newtons (N).
If the force of gravity pulling this object downwards is 20 N , its weight
is 20N!
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What
is mass?
The mass of a body is the quantity of matter in it. Mass is measured in
kilograms (kg) and grams (g).
The Earth pulls an object which has a mass of 1 kg with a force of about
10 N. Hence the weight of the object on Earth is 10 N.
The Moon has a smaller mass than that of the Earth. If the object is on
the Moon, it will have a smaller weight (about 1.6N, i.e. 1/6 that on
the Earth).
It is because the Moon pulls it with a smaller force. However, the object
would still have a mass of 1 kg on the Moon.
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