# NCERT Class 8 Science Chapter 12 Friction Extra Questions

## NCERT Class 8 Science Chapter 12 Friction Extra Questions and Answers

Class 8 Science Chapter 12 Extra Questions and Answers – Friction. Here in this Page Class VIII Students can Learn Extra Questions & Answer 12th Chapter Science fully Inside.

We Provided Here Friction Science Chapter 12 Long Answer Type Question, Very Short Type Questions (VSA) / MCQ Type Questions, Short Type Questions (SA). 1) Fill in the blanks:

a) Spring balance is used for measuring the ____ acting on an object. (Force)

b) The frictional force exerted by fluids is called ____. (Drag)

c) ____ reduces friction. (Rolling)

d) Tires are treaded to _____ friction. (Increase)

2) Multiple choice questions:

a) Soles of shoes wear out due to ____?

a) Force b) Friction

Ans. b) Friction

b) Rolling friction is _____ than sliding friction?

a) Larger b) Smaller

Ans. b) Smaller

c) Friction can produce ____?

a) Force b) Heat

Ans. b) Heat

d) Friction can be increased by making a surface ____?

a) Smooth b) Rough

Ans. b) Rough

a) Explain why objects moving in fluids are given special shapes with an example.

Ans. The objects moving in fluids are given special shapes because it is obvious that when objects move through fluids, they have to overcome friction acting on them. In this process they lose energy. Efforts are, therefore, made to minimize friction. For example, birds have to move about in fluids all the time. Their bodies must have evolved to shapes which would make them lose less energy in overcoming friction.

b) State one example for each of rolling friction and sliding friction.

Ans. Rolling friction – Pulling luggage fitted with rollers.

Sliding friction – Rubbing both the hands together to create heat.

c) Explain why a motor mechanic uses grease between the moving parts of a machine.

Ans. A motor mechanic uses grease between the moving parts of a machine to reduce friction in order to increase efficiency. When grease is applied between the moving parts of a machine, a thin layer is formed there and moving surfaces do not directly rub against each other. Interlocking of irregularities is avoided to a great extent. Movement becomes smooth.

a) A: It is always easier to roll than to slide a body over another.

R: Rolling reduces friction.

I.) Both A and R are true and R is the correct explanation of A.

II.) Both A and R are true but R is not the correct explanation of A.

III.) A is true but R is false.

IV.) A is false but R is true.

V.) Both A and R are false.

Ans. I. Both A and R are true and R is the correct explanation of A.

b) A: When a few drops of oil are poured on the hinges of a door, the door moves smoothly.

R: Oil does not reduces friction.

I.) Both A and R are true and R is the correct explanation of A.

II.) Both A and R are true but R is not the correct explanation of A.

III.) A is true but R is false.

IV.) A is false but R is true.

V.) Both A and R are false.

Ans. III. A is true but R is false.

5) We deliberately increase friction by using brake pads in the brake system of bicycles and automobiles. When you are riding a bicycle, the brake pads do not touch the wheels. But when you press the brake liver, these pads arrest the motion of the rim due to friction. The wheel stops moving. You might have seen that kabaddi players rub their hands with soil for a better grip of their opponents. Gymnasts apply some coarse substance on their hands to increase friction for better grip.

a) When you press the brake liver, these pads arrest the motion of the rim due to _____.(Friction)

b) Kabaddi players rub their hands with soil for _____.(a better grip of their opponents)

c) Gymnasts apply some coarse substance on their hands to _____ friction for better grip.

a) Increase b) Decrease

Ans. a) Increase

### More Extra Questions and Answers

Q.1) Fill in the blanks

1) Spring balance is a device used for measuring the force acting on an object.

2) Friction is caused by the irregularities on the two surface is in contact.

3) The force required to keep the object moving with the same speed is a major of sliding friction.

4) If an object started moving it would never stop if there were no friction.

5) Friction can also produced heat.

6) Friction can never be eliminated.

7)When one body rolls over the surface of another body the resistance to its motion is called rolling friction.

8) The rolling friction is smaller than the sliding friction.

9) The frictional force exerted by fluids is called drag.

Q.2) Say whether the following statements are true or false

1) Friction depends on the nature of surface and which they are in contact with.

Ans :True

2) Sliding friction is smaller than static friction.

Ans :True

In case you are missed :- Previous Chapter Extra Questions

3) Gymnast applies some core substance on their hands to increase friction for better grip.

Ans :True

4) The force required to keep the object moving with the same speed is a major of  staticfriction.

Ans :False

5) Friction is caused by the irregularities on the two services in contact.

Ans : True

6) The force of friction is lower if a surface is rough.

Ans :False

Q.3) Define the following

1) Spring balance

Ans :A spring balance is a device used for measuring the force acting on an object.

2) Lubricants

Ans :The substance which reduced friction are called lubricants n

3) Rolling friction

Ans :When one body rolls over the surface of another body the resistance to its motion is called as rolling friction.

4) Drag

Ans :The frictional force exerted by fluids is called drag.

5) Sliding friction

Ans :When one body slides over the another body then friction caused is called a sliding friction.

6) Static friction

Ans :Static friction comes into play when we try to move an object which is at rest.

1) What does friction depends upon?

Ans :Friction depends on the nature of the surface is in which they are contact with.While it is convenient to pull luggage fitted with rollers.Ruling reduces the friction with an object it is easy to roll a body than to slide over another. Does it is convenient to pull luggage fitted with rollers.

2) What is the measure of starting friction?

Ans :The force required to overcome friction at the instant an object start moving from rest is a major of static friction.

3) When can the force of friction be increased?

Ans : If the two services are pressed harder than the force of friction gets increased.

4) Why does the wheel stops moving when we apply brake ?

Ans – When we use brake pads in the brake system of bicycle we increase the friction my using it. But when you press the brake lever these parts arrest the motion of the rim due to friction and the wheel stops moving.

5) Why are objects given the special shape ?

Ans : As objects move through fluids they had to overcome friction acting on them; Where they lose energy. In order to minimise friction objects are given special shape.

In case you are missed :- Next Chapter Extra Questions

Updated: April 5, 2023 — 12:10 pm