# NCERT Solutions for Class 8 Science Chapter 12 – Friction

NCERT Solutions for Class 8 Science Chapter 12-Friction, contains solutions to various questions in Exercise for Chapter 12.  At the end of the Solutions, all the keywords and Notes which are important to understand Science Chapter 12-Friction, have been explained in a simple and easy to understand manner. We are providing NCERT Solutions for Class 8 all subjects which can be accessed by clicking here.

NCERT Solutions for Class 8 Science Chapter 12-Friction– Solutions to Question 1 and Question 2

NCERT Solutions for Class 8 Science Chapter 12-Friction– Solutions to Question 3 and Question 4

NCERT Solutions for Class 8 Science Chapter 12-Friction– Solutions to Question 4 to Question 8

NCERT Solutions for Class 8 Science Chapter 12-Friction– Solutions to Question 8 to Question 10

NCERT Solutions for Class 8 Science Chapter 12-Friction–Definition of the Keywords-Friction, Lubricants, Rolling friction, Sliding friction, Fluid friction and Drag.

NCERT Solutions for Class 8 Science Chapter 12 Friction, Exercises includes –Fill in the blanks, Choose the correct option and Questions/ Answers  which helps you to understand the topic covered in Friction Class 8, in a better manner to help you to score good marks in your examinations.

### NCERT Solutions for Class 8 Science Chapter 12 Friction– NCERT Exercises

Question 1

Fill in the blanks:

(a) Friction opposes the _______ between the surfaces in contact with each other.

(b) Friction depends on the _______ of surfaces.

(c) Friction produces _______.

(d) Sprinkling of powder on the carrom board ______ friction.

(e) Sliding friction is _______ than the static friction.

(a) Friction opposes the relative motion between the surfaces in contact with each other.

(b) Friction depends on the nature of surfaces.

(c) Friction produces heat.

(d) Sprinkling of powder on the carrom board reduces friction.

(e) Sliding friction is less than the static friction.

Question 2

Four children were asked to arrange forces due to rolling, static and sliding frictions in a decreasing order. Their arrangements are given below.

Choose the correct arrangement.

(a) Rolling, static, sliding

(b) Rolling, sliding, static

(c) Static, sliding, rolling

(d) Sliding, static, rolling

(c) Static, sliding, rolling

Question 3

Alida runs her toy car on dry marble floor, wet marble floor, newspaper and towel spread on the floor. The force of friction acting on the car on different surfaces in increasing order will be :

(a) Wet marble floor, dry marble floor, newspaper and towel.

(b) Newspaper, towel, dry marble floor, wet marble floor.

(c) Towel, newspaper, dry marble floor, wet marble floor.

(d) Wet marble floor, dry marble floor, towel, newspaper

(a)Wet marble floor, dry marble floor, newspaper and towel

Question 4

Suppose your writing desk is tilted a little. A book kept on it starts sliding down. Show the direction of frictional force acting on it.

Let the block shown in the figure represent the book. The direction of friction is shown acting in the direction opposite to the direction of motion.

When the table is tilted then the sliding frictional force acts on the book by the table and it acts in the opposite direction to the motion of the book so as to stop the relative motion in between the two bodies.

Question 5

You spill a bucket of soapy water on a marble floor accidently. Would it make it easier or more difficult for you to walk on the floor? Why?

It will make it difficult for us to walk on the floor which is wet with soapy water because soapy water decreases the friction on the floor. When we walk on the floor, it is the friction which helps us maintain our grip and foothold on the floor. When the friction is reduced, it causes us trouble to walk.

Question 6

Explain why sportsmen use shoes with spikes.

Sportsmen use shoes with spikes on them in order to increase the friction acting between the shoes and the ground. The increased friction enables them to play without the risk of slipping or falling on the ground as spikes increase friction, hence allowing better grip on the ground.

Question 7

Iqbal has to push a lighter box and Seema has to push a similar heavier box on the same floor. Who will have to apply a larger force and why?

Seema will have to apply a larger force because the heavier box presses hard against the floor because of its greater weight. As a result, it increases the friction acting on it when pushed. Therefore, Seema will have to apply greater force to overcome the greater friction.

Question 8

Explain why the sliding friction is less than the static friction.

Friction between two bodies acts when the irregularities present in between the surface of the two bodies come in contact and get interlocked. When a body is sliding then it gets little time to form those interlocks as compared to when it is at rest and the interlocks are almost perfect. That is the reason why sliding friction is slightly lower than the static friction.

Question 9

Give examples to show that friction is both a friend and a foe.

Friction is a friend because:

1. It helps us to grip and catch different substances.
2. We are able to walk on the ground due to friction
3. It enables us to write on paper, blackboard etc.
4. Brakes work due to friction between the tyres and braking system
5. Things do no automatically move from their place due to friction

Friction is a foe because:

1. Friction causes wear and tear in objects
2. It does not allow free movement of objects
3. It generates heat in moving parts of a machine
4. Many machine parts are damaged and need repairing due to friction
5. Space shuttles waste tonnes of fuel overcoming friction of air.

Question 10

Explain why objects moving in fluids must have special shapes.

When body moves through a fluid, it experiences a viscous force acting on it called the drag force. In order to minimize this force, the bodies moving through the fluids are streamlined with pointed fronts and broader middle which gets tapered at the back, which allows the body to move much freely inside water.

### Topics Covered in Chapter 12 FrictionClass 8 Science :-

• Force of Friction
• Factors affecting Friction
• Friction : A Necessary Evil
• Increasing and Reducing Friction
• Wheels Reduce Friction
• Fluid Friction

### Important Terms Relevant to understand NCERT Solutions for Class 8 Science Chapter 12 – Friction

Friction: Friction is the resistive force acting between two bodies due to the relative motion between them.

Lubricants: A substance which is applied between surfaces in order to reduce friction in between them which ultimately reduces the generation of heat between them is called a lubricant.

Rolling friction: Rolling friction is the resistive force that slows down the motion of a rolling body. It is mainly caused by non-elastic effects.

Sliding friction: Sliding friction is the resistive force which develops when two surfaces slide against each other. It is also known as kinetic friction and is intended to stop the relative motion of the surfaces.

Fluid friction: Fluid friction is the frictional force that acts between the different layers of fluids due to the viscous force between them. It is an internal frictional force.

Drag: The frictional force exerted by the fluids is also referred to as drag.