# NCERT solutions for Science Exemplar Class 8 chapter 12 - Friction [Latest edition]

## Chapter 12: Friction

Multiple Choice Questions [Pages 68 - 69]

### NCERT solutions for Science Exemplar Class 8 Chapter 12 Friction Multiple Choice Questions [Pages 68 - 69]

Multiple Choice Questions | Q 1. | Page 68

Whenever the surfaces in contact tend to move or move with respect to each other, the force of friction comes into play

• only if the objects are solid.

• only if one of the two objects is liquid.

• only if one of the two objects is gaseous.

• irrespective of whether the objects are solid, liquid or gaseous.

Multiple Choice Questions | Q 2. | Page 68

In figure, a boy is shown pushing the box from right to left. The force of friction will act on the box

• from right to left (←)

• from left to right (→)

• vertically downwards (↓)

• vertically upwards (↑)

Multiple Choice Questions | Q 3. | Page 68

To sharpen the blade of a knife by rubbing it against a surface, which of the following will be most suitable?

• Stone

• Plastic block

• Wooden block

• Class block

Multiple Choice Questions | Q 4. | Page 68

A toy car released with the same initial speed will travel farthest on

• muddy surface

• polished marble surface

• cemented surface

• brick surface

Multiple Choice Questions | Q 5. | Page 69

If we apply oil on door hinges, the friction will

• increase

• decrease

• disappear altogether

• will remain unchanged

Multiple Choice Questions | Q 6. | Page 69

Which of the following statements is incorrect?

• Friction acts on a ball rolling along the ground

• Friction acts on a boat moving on water

• Friction acts on a bicycle moving on a smooth road

• Friction does not act on a ball moving through air

Multiple Choice Questions | Q 7. | Page 69

A boy rolls a rubber ball on a wooden surface. The ball travels a short distance before coming to rest. To make the same, ball travel longer distance before coming to rest, he may

• spread a carpet on the wooden surface

• cover the ball with a piece of cloth

• sprinkle talcum powder on the wooden surface

• sprinkle sand on the wooden surface

Multiple Choice Questions | Q 8. | Page 69

In a large commercial complex there are four ways to reach the main road. One of the path has loose soil, the second is laid with polished marble, the third is laid with bricks and the fourth has gravel surface. It is raining heavily and Paheli wishes to reach the main road. The path on which she is least likely to slip is

• loose soil

• polished marble

• bricks

• gravel

Very Short Answer Questions [Pages 69 - 70]

### NCERT solutions for Science Exemplar Class 8 Chapter 12 Friction Very Short Answer Questions [Pages 69 - 70]

Very Short Answer Questions | Q 9. | Page 69

Two blocks of iron of different masses are kept on a cemented floor as shown in the figure. Which one of them would require a larger force to move it from the rest position?

Very Short Answer Questions | Q 10. | Page 70

Will force of friction come into play when a rain drop rolls down a glass window pane?

Very Short Answer Questions | Q 11. | Page 70

Two boys are riding their bicycles on the same concrete road. One has new tyres on his bicycle while the other has tyres that are old and used. Which of them is more likely to slip while moving through a patch of the road which has lubricating oil spilled over it?

Very Short Answer Questions | Q 12. | Page 70

Figure shows two boys applying force on a box. If the magnitude of the force applied by each is equal, will the box experience any force of friction?

Very Short Answer Questions | Q 13. | Page 70

Imagine that an object is falling through a long straight glass tube held vertical, air has been removed completely from the tube. The object does not touch the walls of the tube. Will the object experience any force of friction?

Short Answer Questions [Pages 70 - 71]

### NCERT solutions for Science Exemplar Class 8 Chapter 12 Friction Short Answer Questions [Pages 70 - 71]

Short Answer Questions | Q 14. | Page 70

You might have noticed that when used for a long time, slippers with rubber soles become slippery. Explain the reason.

Short Answer Questions | Q 15. | Page 70

Is there a force of friction between the wheels of a moving train and iron rails? If yes, name the type of friction. If an air cushion can be introduced between the wheel and the rail, what effect will it have on the friction?

Short Answer Questions | Q 16. | Page 71

Cartilage is present in the joints of our body which helps in their smooth movement. With advancing age, this cartilage wears off. How would this affect the movement of joints?

Short Answer Questions | Q 17. | Page 71

While playing tug of war, Preeti felt that the rope was slipping through her hands. Suggest a way out for her to prevent this.

Short Answer Questions | Q 18. | Page 71

The handle of a cricket bat or a badminton racquet is usually rough. Explain the reason.

Short Answer Questions | Q 19. | Page 71

Explain why the surface of mortar and pestle (silbatta) used for grinding is etched again after prolonged use.

Short Answer Questions | Q 20. | Page 71

A marble is allowed to roll down an inclined plane from a fixed height. At the foot of the inclined plane, it moves on a horizontal surface (a) covered with silk cloth (b) covered with a layer of sand and (c) covered with a glass sheet. On which surface, will the marble move the shortest distance. Give reason for your answer.

Short Answer Questions | Q 21. | Page 71

A father and son pushed their car to bring it to the side of road as it had stalled in the middle of the road. They experienced that although they had to push with all their might initially to move the car, the push required to keep the car rolling was smaller, once the car started rolling. Explain.

### NCERT solutions for Science Exemplar Class 8 Chapter 12 Friction Long Answer Questions [Page 72]

Long Answer Questions | Q 22. | Page 72

When the cutting edge of a knife is put against a fast rotating stone to sharpen it, sparks are seen to fly. Explain the reason.

Long Answer Questions | Q 23. | Page 72

We have two identical metal sheets. One of them is rubbed with sand paper and the other with ordinary paper. The one rubbed with sand paper shines more than the other. Give reason.

Long Answer Questions | Q 24. | Page 72

While travelling on a rickshaw, you might have experienced that if the seat cover is very smooth, you tend to slip when brakes are applied suddenly. Explain.

Long Answer Questions | Q 25. | Page 72

Two friends are trying to push a heavy load as shown in the figure below. Suggest a way which will make this task easier for them.

## NCERT solutions for Science Exemplar Class 8 chapter 12 - Friction

NCERT solutions for Science Exemplar Class 8 chapter 12 (Friction) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. Shaalaa.com has the CBSE Science Exemplar Class 8 solutions in a manner that help students grasp basic concepts better and faster.

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Concepts covered in Science Exemplar Class 8 chapter 12 Friction are Force of Friction, Effects of Friction, Increasing and Reducing Friction, Kinds of Friction, Fluid Friction, Friction - A Necessary Evil, Factors Affecting Friction.

Using NCERT Class 8 solutions Friction exercise by students are an easy way to prepare for the exams, as they involve solutions arranged chapter-wise also page wise. The questions involved in NCERT Solutions are important questions that can be asked in the final exam. Maximum students of CBSE Class 8 prefer NCERT Textbook Solutions to score more in exam.

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