# Laws of Motion Exe-3E Very Short Answer Physics Class-9 ICSE Selina Publishers

Laws of Motion Exe-3E Gravitation Very Short Answer Type for Class-9 ICSE Concise Physics. There is the solutions of Very short Answer type Questions of your latest textbook which is applicable in 2023-24 academic sessionVisit official Website CISCE for detail information about ICSE Board Class-9.

## Laws of Motion Exe-3E Gravitation Very Short Answer

(ICSE Class – 9 Physics Concise Selina Publishers)

 Board ICSE Class 9th Subject Physics Writer / Publication Concise selina Publishers Chapter-3 Laws of Motion Exe – 3E Gravitation Topics Solution of Exe-3(E) Very Short Answer Type Academic Session 2023-2024

### Exe-3E Gravitation Very Short Answer Type

Ch-3 Laws of Motion Physics Class-9 ICSE Concise

Page 88

#### Question 1. State Newton’s law of gravitation.

Every particle in the universe attracts every other particle with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them, and the direction of the force is along the line joining the masses.

#### Question 2. State whether the gravitational force between two masses is attractive or repulsive?

Gravitational force is always attractive.

#### Question 3. Write an expression for the gravitational force of attraction between two bodies of masses m1 and m2 separated by a distance r.

F∈ (Gm x M)/d²

Here G is a constant of proportionality called the universal gravitational constant.

#### Question 4. How is the gravitational force between two masses affected if the separation between them is doubled?

F∈ (Gm x M)/d²

If the distance between the masses becomes half, the force reduces to one-fourth.

#### Question 5. Define gravitational constant G.

The gravitational constant is defined as the force of attraction between two bodies of unit mass separated by a unit distance.

#### Question 6. Write the numerical value of gravitational constant G with its S.I. unit.

The value of G in the S.I. system is 6.67 x 10-11Nm2kg-2.

#### Question 7. Define the term acceleration due to gravity? Write its S.I. unit.

The rate at which the velocity of a freely falling body increases is called acceleration due to gravity. Its S.I. unit is m/s2.

#### Question 8. Write down the average value of g on Earth’s surface.

The average value of ‘g’ on the Earth’s surface is 9.8 m/s2.

#### Question 9. How are g and G related?

Acceleration due to gravity (g) is directly proportional to universal gravitational constant (G).

(Laws of Motion Exe-3E Very Short Class-9 ICSE)

#### Question 10. A body falls freely under gravity from rest and reaches the ground in time t. Write the expression for the height fallen by the body.

Initial velocity, u = 0.

Time taken = t.

Acceleration due to gravity = g.

Let ‘h’ be the height fallen.

#### Question 11. A body is thrown vertically upwards with an initial velocity u. Write the expression for the maximum height attained by the body.

If a body is thrown vertically up with an initial velocity u to a height h, then there will be retardation (a = g).

At the highest point, the final velocity v = 0.

Thus, from the third equation,

#### Question 12. State the S.I. units of (a) mass and (b) weight.

The S.I. unit of mass is kg and that of weight is newton.

#### Question 13. The value of g at the centre of Earth is zero. What will be the weight of a body of mass m kg at the centre of the Earth?

W = mg

At the centre of Earth, g = 0.

Therefore, W = 0.

#### Question 14. Which of the following quantity does not change by change of place of a body : mass or weight?

Mass of a body is always constant.

—  : End of Laws of Motion Exe-3E Gravitation Very Short Answer Type  Solutions :–

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