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NCERT · Class 9 · Science

Chapter 9: Gravitation

Practice each question, then open the answer or worked solution.

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Exercise-10.3

Textbook page 138 · 2 questions
Q1Written answer

What are the differences between the mass of an object and its weight?

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Worked solution

The differences between the mass of an object and its weight are tabulated below.

Mass Weight
Mass is the quantity of matter contained in the body. Weight is the force of gravity acting on the body.
It is the measure of inertia of the body. It is the measure of gravity.
It only has magnitude. It has magnitude as well as direction.
Mass is a constant quantity. Weight is not a constant quantity. It is different at different places.
Its SI unit is kilogram (kg). Its SI unit is the same as the SI unit of force, i.e., Newton (N).
Q2Written answer

Why is the weight of an object on the moon 1/6th its weight on the earth?

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Worked solution

The mass of the moon is 1/100 times and its radius 1/4 times that of earth. As a result, the gravitational attraction on the moon is about one-sixth when compared to earth. The moon’s gravitation force is determined by the mass and the size of the moon. Hence, the weight of an object on the moon is 1/6th its weight on the earth. The moon is far less massive than the Earth and has a different radius(R) as well.