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Physics
Weight of objects

In daily life we actually mean mass when we say ‘weight’. We do not differentiate these two
terms, saying, for example, ‘weigh 2 kg of apples’. Actually this is wrong. When we weigh
ourselves on the scales, they show the force we exert on them.

Gravity around the Solar System and the universe
The force of gravity is not unique to the Earth. In fact, it exists across the entire universe
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and affects all physical bodies in it. All objects in the universe – galaxies, stars, the Sun and
planets, the Earth and the Moon, ships in the sea, even sand particles, are all attracted to
each other via the force of gravity. All physical bodies/objects/particles that have mass are
affected by gravity. It just depends on how large they are. The larger their mass, the larger
the force of gravity they exert on other physical bodies/objects/particles. However, the
larger the distance between them, the smaller the force of gravity (or gravitational force).

The force of gravity acts between all objects.

If mass increases, the force of gravity increases.

If distance increases, the force of gravity decreases.

OVER TO YOU!

1. Explain the difference between mass and weight. Give two examples.

2. How does the force of gravity acting on two stones of equal mass compare, if
one stone is on the Kapchagay Reservoir bank and the other is on the peak of the
Khan-Tengri mountain (7010 m high with the ice cap)?

3. Why is it easier for Opportunity to move a rock on Mars than on Earth?
4. The International Space Station orbits the Earth at an altitude of 400 km. Does an
astronaut experience a gravitational force? Explain your answer.

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