Laws of Motion Concise ICSE Class-9 Selina Publishers Solutions Chapter-3 . Step By Step ICSE Selina Concise Solutions of Chapter-3 Laws of Motion  with Exercise-3(A), Exercise-3(B) , Exercise-3(C) ,Exercise-3(D) and Exercise-3(E) including Numerical and MCQ Questions Solved Visit official Website CISCE for detail information about ICSE Board Class-9.

 Board ICSE Publications Selina Publication Subject Physics Class 9th Chapter-3 Laws of Motion Exe-3(A) Book Name Concise Topics Solution of Exe-3(A),  MCQ 3(A),   Exercise-3(B),  MCQ-3(B),     Exercise-3(C),  MCQ-3(C) ,  Numericals-3(C),    Exercise-3(D),  MCQ-3(D) ,  Numericals-3(D),   Exercise-3(E),  MCQ-3(E) ,  Numericals-3(E), Academic Session 2021-2022

## Laws of Motion Concise ICSE Class-9 Selina Publishers Physics Chapter-3

–: Select Topics :–

Exercise-3(A),  MCQ-3(A),

Exercise-3(B),  MCQ-3(B)

Exercise-3(C),  MCQ-3(C)Numericals-3(C),

Exercise-3(D),  MCQ-3(D) ,  Numericals-3(D),

Exercise-3(E),  MCQ-3(E) ,  Numericals-3(E),

Note :-  Before Viewing Selina Concise Physics Solutions of Chapter-3 Laws of Motion Class-9 Physics . Read the whole chapter carefully and Solved all example of Exercise-3 Laws of Motion Class-9 Physics

Page 59

#### Question 1

Explain giving two examples each of :

(a) Contact forces

(b) Non – contact forces

(a) The forces which act on bodies when they are in physical contact are called contact forces.

Example: frictional force and force exerted on two bodies during collision.

(b) The forces experienced by bodies even without being physically touched are called non-contact forces.

Example: Gravitational force and Electrostatic force.

#### Question 2

Classify the following amongst contact and non – contact forces:

(a) Frictional force

(b) Normal reaction force

(c) Force of tension in a string

(d) Gravitational force

(e) Electrostatic force

(f) Magnetic force

Contact force: (a) frictional force (b) normal reaction force (c) force of tension in a string

Non-contact force: (d) gravitational force (e) electric force (f) magnetic force

#### Question 3

Give one example in each case where :

(a) The force is of contact, and

(b) Force is at a distance

(a) Force exerted on two bodies during collision.

(b) Magnetic force between magnetic poles.

#### Question 4

(a) A ball is hanging by string from the ceiling of the roof. Draw a neat labelled diagram showing the forces acting on the ball and the string.

(b) A spring is compressed against a rigid wall. Draw a neat and labeled diagram showing the forces acting on the spring.

(c) A wooden block is placed on a table top. Name the forces acting on the block and draw a neat and labelled diagram to show the point of application and direction of these forces.

A C.

The forces acting on the block are its weight in the downward direction and the normal reaction force due to the table on the upward direction. #### Question 5

State one factor on which the magnitude of a non-contact force depends. How does it depend on the factor stated by you?

The magnitude of non-contact force on two bodies depends on the distance of separation between them.

The force decreases as the distance of separation increases.

The force is inversely proportional to the square of the distance of separation.

Page 60

#### Question 6

The separation between two masses is reduced to half. How is the magnitude of gravitational force between them affected?

The magnitude of gravitational force between two masses will become four times as gravitational force varies inversely as the square of distance of separation.

#### Question 7

State the effects of a force applied on

A non-rigid, and

A rigid body.

How does the effect of the force differ in the two cases?

A force when applied on a non-rigid body changes the inter-spacing between its constituent particles and therefore causes a change in its dimensions and can also produce motion in it.

On the other hand, a force when applied on a rigid body, does not change the inter-spacing between its constituent particles and therefore it does not change the dimensions of the body but causes motion in it

#### Question 8

Give one example in each of the following cases where a force:

(a)Stops a moving body.

(b)Moves a stationary body.

(c) Changes the size of a body.

(d) Changes the shape of a body.

(a)A fielder on the ground stops a moving ball by applying a force with his hands.

(b) The pull exerted by horse makes a cart moves.

(c) In a cycle pump, when the piston is lowered, the air is compressed to occupy a less volume.

(d) On pressing a piece of rubber, its shape changes.

Page 60

#### Question 1

Which of the following is a contact force:

(a) Electrostatic force

(b) Gravitational force

(c) Frictional force

(d) Magnetic force

Frictional force is a contact force.

#### Question 2

The non – contact force is :

(a) Force of reaction

(b) Force due to gravity

(c) Tension in string

(d) Force of friction