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Class 9 Science gravitation extra questions

                                                            Class 10 Science

                                       Chapter – 10 Gravitation

                                        Extra questions

One word Questions –

Q- 1 The universal law of gravitation was given by –

Ans – Newton

Q- 2 The tidal waves in the sea are primarily due to –

Ans – Gravitation effect of moon on earth

Q- 3 If the radius of earth were to shrink by 1%, its mass remaining the same, the acceleration due to gravity on earth’s surface would –

Ans – Increase      ( R decreases, g increases  g = GM/R² )

Q- 4 In the relation F = GMm/R² , the quantity G is –

Ans – Universal constant of nature

Q- 5    10 kg weight means –

Ans –  98 N    ( W = mg            = 10 x 9.8    = 98 N)

Q- 6 The value of quantity G in the law of gravitation –

Ans – is independent of mass and radius of earth

Q- 7 The value of g is maximum at –

Ans – Poles of the earth.

Q- 8 The weight of an object at the centre of the earth of radius R is –

Ans – Zero

Q- 9 The SI unit of g is –

Ans – m/s²

Q- 10 The SI unit of G is –

Ans – N kg²/m²

Q- 11 An object weighs 10 N when measured on the surface of earth. What should be its weight on moon ?

Ans – 1.67 N    ( Weight of an object on the moon is 1/6th of  weight of an object on the earth so   10/6 = 1.67 N)

Q- 12 ‘G’ stands for –

Ans – Universal Gravitational Constant

Q- 13 ‘g’ stands for –

Ans – Acceleration due to gravity

Q- 14 When a body is dropped from a height, what is its initial velocity?

Ans – Zero

Q- 15 When a body is thrown vertically upwards, what is its final velocity?

Ans – Zero

Q- 16 Is weight a force –

Ans – Yes      ( F = W = mg)

Q- 17 If the mass of a body is 9.8 kg on the earth, what would be its mass on the moon ?

Ans – 9.8 kg  ( It will be remain same on the moon as mass of any object will be constant everywhere)

Q- 18 At what place on the earth’s surface is the weight of the body minimum?

Ans – At the equator

Q- 19 Value of G –

Ans – 6.67 x 10-11 Nm²/kg²

Q- 20 Value of g –

Ans – 9.8 m/s²

Very Short questions –

Q- 1  Why is ‘G’ called the universal gravitational constant –

Ans – The constant ‘G’ is universal because it is independent of the nature and sizes of bodies, the space where they are kept and at the time at which the force is considered.

Q- 2 The earth is acted upon by gravitation of sun, even though it does not fall into the Sun. Why?

Ans – The gravitational force is responsible for providing the necessary centripetal force which binds the earth to move around the Sun at the its orbit or a defined path. So earth does not fall into the Sun.

Q- 3 What keeps the moon in uniform circular motion around the earth?

Ans – Gravitation force which is responsible for centripetal force which binds moon to keep around the earth in uniform circular motion.

Q- 4 Why can one jump higher on the surface of the moon than on the earth?

Ans – The value of acceleration due to gravity(g) on the moon’s surface is nearly 1/6th to that of the surface of the earth.

Q- 5 How is gravitation different from the gravity?

Ans – Gravitation is the force of attraction between any two bodies while gravity is the acceleration due to gravitational force.

Q- 6 If the distance between the objects is doubled, what happens to the force between two objects ?

Ans – The gravitational force will be 1/4th of the original value,

    F = GMm/d²

    If d = 2d

    F’ = GMm/(2d)²

   F’ = F/4

Q- 7 If the mass of the both objects is doubled, what happens to the force between two objects ?

Ans –   It will be four times of the original value.

F = GMm/d²

F’ = G 2M x 2m/d²

F’ = 4GMm/d²

F’ = 4F

Q- 8 SI unit of mass and weight –

Ans – SI unit of mass is kilogram, SI unit of weight is Newton.

Q- 9 What do we call the gravitational force between the earth and an object ?

Ans – Force of gravity or gravity.

Q- 10 Newton’s law of gravitation is applicable to –

Ans – All bodies in the universe

Q- 11 A body falling under gravity moves with a constant-

Ans – Acceleration

Q- 12 An apple falls from a tree because of gravitational attraction between the earth and apple. If F1 is the magnitude of force exerted by the earth on the apple and F2 is the magnitude of force exerted by apple on the earth, then –

Ans – F1 and F2 both are equal

Q- 13 Why does formation of tides takes place in sea or ocean?

Ans – The tides in the sea formed by the rising and falling of water level are due to the gravitational force of attraction which the sun and moon exert on the water surface in the sea.

Q- 14 What does a small value of G indicate –

Ans – A small value of G indicates that the force of gravitational attraction between two ordinary sized objects is a very weak force.

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