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CBSE Class 8 Science Chapter 10 Sound Fill In The Blanks

Question 1. Sound is produced by__________ objects.
Answer: Vibrating

Question 2. The other name of human voice box is__________
Answer: Larynx

Question 3. Sound can travel in and __________
Answer: Solids, liquids, gases

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Question 4. The loudness of normal breathing of humans is__________ dB.
Answer: 10

Question 5. Vibration is repeated__________ and motion.
Answer: To, From

Question 6. A tight membrane vibrates at a much__________ frequency than a loose one.
Answer: Higher

Question 7. Sound which is pleasing to our ears is called__________
Answer: Music

Question 8. A person having partial hearing loss can hear properly by using a device called__________ aid.
Answer: Hearing

Question 9. The speed of sound in air is__________
Answer: 344m/s

Question 10. Muscles attached to the vocal cords can make the cords ___________or__________
Answer: Tight, loose

Question 11. The pitch of the sound depends on the_____________
Answer: Frequency

Question 12. The time taken by an object to complete one oscillation is called
Answer: Period

Question 13. The amount of vibration determines loudness.
Answer: Amplitude

Question 14. The unit of frequency is
Answer: Hertz

Question 15. Unwanted sound is called
Answer: Noise

Question 16. The frequency of vibration determines the Shrillness of a sound.
Answer: Frequency 

CBSE Class 8 Science Chapter 10 Sound True Or False

Question 1. The intensity of the sound depends on the frequency of the wave.
Answer: True

Question 2. In human beings, the vibration of the vocal cords produces sound.
Answer: True

Question 3. The higher the amplitude of vibration, the lower the pitch.
Answer: False

Question 4. Regular vibrations produce musical sounds.
Answer: True

Question 5. Shriller sound has a higher frequency.
Answer: True

Question 6. Plantation along the roadside can reduce noise pollution.
Answer: True

Question 7. Man cannot hear the sound of bats.
Answer: True

Question 7. The speed of sound is more than the speed of light.
Answer: False

Question 8. The sound travels fastest in solids.
Answer: True

Question 9. The sound waves produced by the bats are infrasonic.
Answer: False

Question 10. Sound cannot travel in a vacuum.
Answer: True

Question 11. The number of oscillations per second of a vibrating object is called its period.
Answer: False; The number of oscillations per second of a vibrating object is called frequency.

Question 12. If the amplitude of vibration is large, the sound is feeble.
Answer: False; Amplitude of vibration is directly proportional to the loudness of sound.

Question 13. For human ears, the audible range is 20 Hz to 20000 Hz.
Answer: True

Question 14. The lower the frequency of vibration, the higher the pitch.
Answer: False; The lower the frequency of vibration, the lower the pitch.

Question 15. Unwanted or unpleasant sound is termed as music.
Answer: False; Unwanted or unpleasant sound is termed as noise.

Question  16. Noise pollution may cause partial hearing impairment.
Answer: True

CBSE Class 8 Science Chapter 10 Sound Match The Columns

Answer: 1-3, 2-3,3-1,4-5,5-4

CBSE Class 8 Science Chapter 10 Sound

The following questions consist of two statements- Assertion (A) and Reason (R). Answer these questions by selecting the appropriate options given below.

1. Both A and R are true, and R is the correct explanation of A.
2. Both A and R are true, but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false, but R is true.

Question 10.

Assertion (A) Sound travels more slowly through liquid than.
Reson (R) Thu moloculon In farther from onch other.

Answer: 1. Both A and R are true, and R is the correct explanation of A.

Question 11.

Assertion (A): The sound of women is shriller than that of men. Ronson (R) The pitch of the sound depends on the frequency of the sound.
Answer: 2. Both A and R are true, but R is not the correct explanation of A.

The following questions consist of two statementsAssertion (A) and Reason (R). Answer these questions by selecting the appropriate option given below

1. Both A and R are true, and R is the correct explanation of A.
2. Both A and R are true, but R is not the correct explanation of A.
3. A is true, but R is false.
4. A is false, but R is true.

Question 1. Assertion (A) Astronauts in space can hear each other. Reason (R) Loud sounds have high amplitude.
Answer: 4. A is false because sound needs a medium to travel, but there is no medium in space. R is correct. Hence, the correct option is (d).

Question 2. Assertion (A) Tabla, sitar, flute, and harmonium are musical instruments. Reason (R) Sound is produced by vibrations in musical instruments.
Answer: Both A and R are correct because, without vibration, sound cannot be produced. Hence, the correct option is (a).

Question 3. Assertion (A) Frequency is measured in hertz (Hz). Reason (R) Lower the frequency, the higher the pitch of
The sound.
Answer: R is false because for higher frequency pitch of the sound is higher. Hence, the correct option is (c).

Question 4. Assertion (A) Human beings cannot hear sounds less than 20 Hz. Reason (R)The  Audible range of humans is 20 Hz to 20 KHz.
Answer: The audible range of sound for human beings is indeed from 20 Hz and 20 kHz. So, both A and R are correct, and R is the correct explanation. Hence, the correct option is (a).

CBSE Class 8 Science Chapter 9 Friction Multiple Choice Questions

Question 1. In the figure, a boy is shown pushing the box from right to left.

The force of friction will act on the box

1. From right to left (←)
2. From left to right (→)
3. Vertically downwards (↓)
4. Vertically upwards (↑)

Answer: 2. From left to right (→)

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Question 2. To sharpen the blade of a knife by rubbing it against a surface, which of the following will be most suitable?

1. Stone
2. Plastic block
3. Wooden block
4. Glass block

Answer: 1. Stone

Question 3. A toy car released with the same initial speed will travel the farthest on

1. Muddy Surface
2. Polished Marble Surface
3. Cemented Surface
4. Brick Surface

Answer: 2. Polished Marble Surface

Question 4. 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 a longer distance before coming to Rest he may

1. Spread a carpet on the wooden surface
2. Cover the ball with a piece of cloth
3. Sprinkle talcum powder on the wooden surface
4. Sprinkle sand on the wooden surface

Answer: 3. Sprinkle talcum powder on the wooden surface

Question 5. It is difficult to walk on a well-polished floor because the friction between our feet and the floor is

1. Increased
2. Reduced
3. Same
4. None of these

Answer: 2. Reduced

Question 6. A student wants to move a heavy block from one place to another. What method should the student apply to reduce the effort?

1. Pull the block using a rope
2. Place wheels under the block
3. Slide the block along the surface
4. Apply oil to the bottom of the block

Answer: 2. Place wheels under the block

Question 7. The picture shows four types of shoe soles.

Which shoe sole provides the best grip and friction while walking?

1. Sole 1
2. Sole 2
3. Sole 3
4. Sole 4

Answer: 4. Sole 4

Question 8. We can increase the friction by

1. Polishing
2. Making grooves and treads
3. Streamlining
4. Using a ball bearing

Answer: 2. Making grooves and treads

Question 9. If we apply oil to the door hinges, the friction will

1. Increase
2. Decrease
3. Disappear altogether
4. Will remain unchanged

Answer: 2. Decrease

CBSE Class 8 Science Chapter 9 Friction Multiple Choice Questions

Question 10. Fine powder is poured on the carromboard to

1. Increase Friction
2. Decrease Friction
3. Both (a) and (b)
4. None of these

Answer: 2. Decrease Friction

CBSE Class 8 Science Chapter 9 Friction Long Answer Questions

Question 1. Raju wanted to find out which one of the four surfaces produces the greatest friction. He pushed the same toy car on the four surfaces, separately.

Raju noted the distance travelled by car on each surface before stopping.

1. On which surface did the car experience the greatest friction?

1. Surface 1
2. Surface 2
3. Surface 3
4. Surface 4

Answer: 3. Surface 3

2. What must be kept the same in the activity to compare the distances travelled by the car?
Answer: The Toy car and pushing force must be kept the same in the activity to compare the distance travelled by the car.

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3. What will happen to the car if it continues to move on the surface for 1 h?

1. The wheels will get hard.
2. The wheels will become hot.
3. The wheels will shrink in size.
4. The wheels will change shape

Answer: 2. The wheels will become hot.

Question 2. The picture shows four different rubber tubes.

1. Which tube will experience the least friction while rolling on a surface? Explain your answer.
Answer: Tube 2 experiences the least friction while rolling on n surface because the area of contact between the two surfaces is less in the case of Tube 2.

2. Which of these would affect the amount of friction generated on a moving object? Circle ‘Yes’ or ‘No’ for the correct response.

Answer: (a) Yes, (b) Yes, (c) Yes

Question 3. Anshu lets a marble roll freely on four rough wooden planks. The table shows the time taken by the marble to reach the bottom of each plank.

1. What could be the value of X in the table?

1. 2s
2. 3s
3. 4s
4. 5s

Answer: 4. 5s

2. Anshu polished all four planks to smooth the surfaces. She repeated her activity on the polished planks. Will there be any change in the results? Explain your answer.

Answer: Yes, results will change. Polishing the surface makes it smooth, then the friction between the marble and the plank decreases, which results in a decrease in the time taken by the marble to reach the bottom.

CBSE Class 8 Science Chapter 9 Friction Short Answer Questions

Question 1. Imagine that an object is falling through a long, straight glass tube held vertically, and 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?
Answer: No, the object will not experience any frictional force because to experience the force of friction, two surfaces must be there, and there is only one surface in this case.

Question 2. While travelling on a rickshaw, you might have experienced that if the seat cover is very smooth, you tend to slip when the brakes are applied suddenly. Explain.
Answer: If the seat cover of the rickshaw is very smooth, then the friction between our body and he seat is very small. Therefore, when the brakes are applied, we tend to slip.

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Question 3. Two boys were riding their bicycles on the same concrete road. Ono has new tires on his bicycle, while the other has tires that are old and used tires. Which of them is more likely to slip while moving through a patch of the road that has lubricating oil spilled over it?
Answer: The hoy having tyres which are old and worn tires are most likely to slip because they will experience less frictional force, which is insufficient to move on the oily road.

Question 4. Explain why

1. A pencil will write on paper but not on glass.
Answer: Since, due to friction, a pencil writes on paper, but there is smoothness on the surface of glass, a pencil cannot write on glass.

2. Climbing a greasy pole is very difficult.
Answer: If a pole is polished with grease, then the surface of pole becomes smoother thus reducing friction. So, climbing a greasy pole becomes tough.

Question 5. The handle of a cricket bat or a badminton racket is usually rough. Explain the reason.
Answer: The handle of a cricket bat or badminton racquet is rough, so that while playing, the bat or badminton racquet does not slip away from the hands of the player. Roughness is responsible for the frictional force, without which gripping is not possible.

Question 6. Is there a force of friction between the wheels of a moving train and the 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?
Answer: Yes, there is always a force of friction between the wheels of a moving train and the iron rails. The name of this friction is rolling friction, since the wheels are rolling on the track. On introducing an air cushion, the frictional force becomes less, since there is no contact between the rails and wheels.

Question 7. A father and son pushed their car to the side of the 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.
Answer: When the car is at rest, we have to apply a greater force because the value of static friction is greater. As the car starts moving, the friction changes into rolling friction, which is always less than the previous one. So, we have to exert a lesser force to keep it in motion.

Question 8. 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.
Answer: Due to the friction between the knife and the stone, the temperature of the knife and hence the stone increases, and it increases to such a level that sparks are produced, which can be seen while sharpening it.

Question 9. 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?
Answer: Cartilage present in the joints ofour body reduces friction during the movement of joints. But on wearing off this cartilage, the force of friction increases, due to which the smoothness of movement decreases, and one feels joint pain.

Question 10. Explain why the surface of the mortar and pestle (silbatta) used for grinding is etched again after prolonged use.
Answer: After prolonged use, the mortar and pestle loose their roughness, due to which frictional force reduces and it does not work properly. So, we have to etch it to make it rough again.

Question 11. You might have noticed that when used for a long time, slippers with rubber soles become slippery. Explain the reason.
Answer: It is due to the continuous rubbing of the soles with the ground; the spikes on the soles get damaged slowly, and the soles become slippery.

Question 12. Explain which principle Is Involved in machine belts.
Answer: In many machines (like flour mills), belts are used to drive wheels for running the machines. Greater friction is required between the belts and machine wheels, so that the belts can drive the machine wheels properly without slipping off the wheels. So, to increase friction, machine belts are made up of special materials having rough surfaces.

Question 13. 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 a reason for your answer.

Answer: Marble will move the shortest distance on the layer of sand because it will exert a greater force of friction on the marble and other two surfaces like silk cloth and glass sheet will exert a lesser friction force comparatively.

Question 14. While playing tug of war, Preeti felt that the rope was slipping through her hands. Suggest a way out for her to prevent this.

Answer: To prevent slipping of the rope from hands, Preeti has to make her hands somewhat non-smooth, so she can rub her hands by introducing sand between them.

CBSE Class 8 Science Chapter 4 Combustion And Flame Review Exercise Multiple Choice Questions

Question 1. Combustion is a process that

1. Releases Light And Heat
2. Absorbs Light And Heat
3. Produces Only Heat
4. Produces Only Light

Answer: 1. Releases Light And Heat

Question 2. Combustion is generally

1. A Physical Process
2. A Chemical Process
3. Both 1 And 2
4. None Of These

Answer: 2. A Chemical Process

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Question 3. The product(s) of combustion is or are

1. Only Oxygen
2. Oxygen And Water
3. Carbon Dioxide And Water
4. Only Carbon Dioxide

Answer: 3. Carbon Dioxide And Water

Question 4. Magnesium ribbon, on burning in air, produces

1. Magnesium Oxide, Water, And Light
2. Magnesium Oxide And Heat
3. Magnesium Oxide, Heat, And Light
4. Magnesium Oxide, Water, And Heat

Answer: 3. Magnesium Oxide, Heat, And Light

Question 5. Coal burns with

1. Flame
2. Only Glow
3. Both Flame And Glow
4. None Of These

Answer: 2. Only Glow

Question 6. The substance that does not burn with flame is

1. LPG
2. Camphor
3. Dry Grass
4. Charcoal

Answer: 4. Charcoal

Question 7. Which of these materials is combustible?

1. Steel
2. Wood
3. Glass
4. Marble

Answer: 2. Wood

Question 8. Which of the following is not a combustible substance?

1. Camphor
2. Glass
3. Straw
4. Alcohol

Answer: 2. Glass

Question 9. A substance that reacts with oxygen, giving heat, is called a combustible substance. Which one of the following is a combustible substance?

1. Iron nail
2. Glass
3. Stone piece
4. Wood

Answer: 4. Wood

Question 10. If a person’s clothes catch fire, the best way to extinguish the fire is to

1. Throw water on the clothes
2. Use a fire extinguisher
3. Cover the person with a woolen blanket
4. Cover the person with a polythene sheet

Answer: 3. Cover the person with a woolen blanket

Question 11. The substance expected to have the highest Ignition temperature out of the following is

1. Kerosene
2. Petrol
3. Coal
4. Alcohol

Answer: 3. Coal

Class 8 Science Chapter 4 Combustion And Flame

Question 12. Water was poured over a large oil fire to extinguish it. What would happen and why?

1. The fire will be put off since water extinguishes fires
2. The fire will spread since oil floats on water
3. The fire will be put off since water dissolves oil
4. The fire will spread since water contains hydrogen, which is a combustible gas

Answer: 2. The fire will spread since oil floats on water

Question 13. In a fire extinguisher, which substance is commonly used for cutting off the oxygen supply to the fire?

1. Water
2. Sand
3. Carbon dioxide
4. Gasoline

Answer: 3. Carbon dioxide

Question 14. On placing an inverted tumbler over a burning candle, the flame extinguishes after some time. This is because of the non-availability of

1. Oxygen
2. Water vapour
3. Carbon dioxide
4. Wax

Answer: 1. Carbon dioxide

Question 15. When a lighted candle placed partly in a trough of water is covered by an inverted glass, water rushes up as shown, and the flame extinguishes. If the above hypothesis is true, what will happen after the candle blows out in the new experimental setup?

1. The mouse will die or show signs of suffocation
2. The mouse will become more active
3. The glass will break, and the mouse will escape
4. There will be no change in the mouse’s behaviour

Answer: 1. The mouse will die or show signs of suffocation

CBSE Class 8 Science Chapter 9 Friction Very Short Answer Questions

Question 1. Will the force of friction come into play when a raindrop rolls down a glass window pane?
Answer: Yes, friction comes into play when two surfaces are in contact, but in a very small amount.

Question 2. If a body is moving on a rough horizontal surface towards the east, then in which direction will the frictional force act?
Answer: Frictional force always acts in the direction opposite to the direction of motion, so it will act towards the west.

Read And Learn More CBSE Class 8 Science Very Short Questions And Answers

Question 3. The figure shows two boys applying force to a box. If the magnitude of the force applied by each is equal, will the box experience any force of friction?

Answer: No, the force applied by both boys is equal. So, the net force will be zero, and hence friction force will not come into play.

Question 4. It is easier to drag a carpet from the floor, but it is difficult to drag the carpet when someone is sitting on it. Explain the reason behind it.
Answer: If the two surfaces are pressed harder, then the force of friction will increase. So, it is easy to drag a carpet when nobody is sitting on it, but when a person is sitting on it, then it produces more friction.

Question 5. Why does a matchstick catch fire when it is rubbed on a rough surface?
Answer: On rubbing the matchstick on a rough surface, the temperature increases due to friction, making the matchstick catch fire.

Question 6. The jar of a mixer becomes hot when it is run for a few minutes. Comment.
Answer: Due to friction, the jar of a mixer becomes hot when it is run for a few minutes.

Question 7. Give n reason for railing friction as n necessary evil.
Answer: Friction is a necessary evil because it causes a lot of wear and tear.

Question 8. Why do kabaddi players rub their hands with soil?
Answer: Kabaddi players rub their hands with soil to increase the friction, so that they can grip the opposing team players firmly.

Question 9. Why do weightlifters apply chalk powder on their palms while lifting weights?
Answer: It increases the roughness in their hand. This provides a better grip while lifting weights.

Question 10. Why are oil, creams, and grease called lubricants?
Answer: Oil, creams and grease, when applied on a surface, make it smooth, thus reducing friction, so these are called lubricants.

Question 11. Can we eliminate friction?
Answer: No, we cannot eliminate friction because it is a characteristic property (molecular property) of a material.

Question 12. What is the special shape of the objects moving in fluids?
Answer: Streamlined shape is the special shape given to objects moving in fluids.

Question 13. Explain fluid friction brief.
Answer: When an object moves in a fluid, the resistance to the movement of the object exerted by the fluid is called fluid friction.

Question 14. Why does an arrow with a pointed tip move faster in the air than one with a flat tip?
Answer: The arrow with a pointed tip suffers small air resistance due to its pointed shape, so it moves faster.

CBSE Class 8 Science Chapter 4 Combustion And Flame Long Answer Questions

Question 1. In an experiment, 4.5 kg of a fuel was completely burnt. The heat produced was measured to be 180000 kJ. Calculate the calorific value of the fuel.
Answer: The amount of heat energy produced on the complete combustion of 1 kg of a fuel is called its calorific value.

Given, total mass of fuel = 4.5 kg

Total heat produced = 180000 kJ

Now, the heat produced in burning 1 kg of fuel, i.e., calorific value

⇒ \(\begin{aligned}
& =\frac{\text { Total heat produced }}{\text { Total mass of fuel }}=\frac{180000}{4.5} \\
& =\frac{180000 \times 10}{45}=\frac{1800000}{45} \\
& =\frac{360000}{9}=40000 \mathrm{~kJ} / \mathrm{kg} \quad \text { (divid }
\end{aligned}\)

Hence, calorific value of fuel =40000 kJ/kg

Question 2. Can the process of rusting be called combustion? Discuss.
Answer: The process of rusting cannot be called combustion because, in this process, no heat and light are produced. For this reason, iron is not considered a combustible substance.

Question 3. Abida and Ramesh were doing an experiment in which water was to be heated in a beaker. Abida kept the beaker near the wick in the yellow part of the candle flame. Ramesh kept the beaker in the outermost part of the flame. Whose water will get heated in a shorter time?
Answer: The water heated by Ramesh will get heated in a shorter time because he kept his beaker near the hottest (non-luminous) zone of the flame. 

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Question 4. Sparkling rods light up when inserted into a flame. The hotter the flame, the quicker the rod lights up. Tito’s picture shows four different zones of a flame.

1. In which zone should a sparkling rod be inserted to light it the fastest?

1. Zone 1
2. Zone 2
3. Zone 3
4. Zone 4

Answer: 1. Zone 1

2. Why does the flame of a candle go off when all the wax melts?

Answer: The flame of the candle goes off because no more wax is available on the candle, which can burn and give flame.

Which zone has unburnt carbon particles?

1. Zone 1
2. Zone 2
3. Zone 3
4. Zone 4

Answer: 3. Zone 3

Question 5. Observe the given picture and answer the following questions

1. Which is the hottest part of the flame in the given figure of a candle?
Answer: A or the outermost part of the flame.

2. Why does the middle zone of the candle flame glow with yellow colour?
Answer: The Middle zone of the candle flame contains unburnt carbon particles, which give the flame a yellow colour.

3. State any two conditions under which combustion takes place.
Answer: The Presence of a supporter of combustion and the presence of a combustible substance are two required conditions for combustion.

Question 6.

(1) In an experiment, 6.5 kg of a fuel was completely burnt. The heat produced was measured to be 1,90,000 KJ. Calculate the calorific value of the fuel in KJ per kg.

Answer: \(\begin{aligned}
& \text { Calorific value }=\text { Energy } / \text { Mass } \\
& =\frac{190000}{65}=29230 \mathrm{~kJ} / \mathrm{kg}
\end{aligned}\)

(2) CNG is a better fuel when compared to petrol or diesel. Regarding the data in the table, evaluate this statement

Answer: CNG produces less carbon monoxide than diesel and produces less greenhouse gas than diesel. Also, CNG has a higher energy density than diesel.

Question 7. The picture shows four types of fire extinguishers. Each extinguisher is suited for specific sources of fire.

1. A tailor has money for any two of the fire extinguishers. Which pair of fire extinguishers should be bought for his tailoring shop?

1. P and Q
2. Q and S
3. P and R
4. S and R

Answer: 3. P and R

2. Fire extinguisher K is suitable for kitchen fires.

1. Which fire extinguisher can perform most of the work of K?

1. P
2. Q
3. R
4. S

Answer: 2. Q

2. How does dumping sand on a fire extinguish the flame?

Answer: Sand absorbs heat and cuts off the oxygen supply, hence, it helps in extinguishing the flame.

Question 9. Although wood has a very high calorific value, we still discourage its use as a fuel. Explain.
Answer: Burning of wood has several disadvantages despite having a high calorific value. These are as follows-

Burning wood produces a lot of smoke, which causes respiratory diseases like asthma.

The cutting down of trees to obtain as a wood fuel leads to deforestation which is very harmful to the environment.

Trees provide us many useful substances. To obtain fuel wood, when trees are cut down, then all useful substances which can be obtained from trees are lost.

Question 10. A forest fire produces a lot of air pollution. Write a brief about the reasons for forest fires.
The reasons for forest fires are as follows

• At high temperatures, sometimes dry grass catches fire, which spreads throughout the forest.
• A campfire may also be a reason for fire.
• Lightning.
• The use of fires by villagers to ward off wild animals.
• Fire was lit intentionally by people living around forests for recreation.
• The friction of bamboo due to high wind velocity and rolling stones.

Question 11. Manu was heating oil to fry potato chips. The cooking oil all of a sudden caught fire, he poured water to extinguish the fire. Do you think, this action was suitable? If yes, why? If not, why not? In such a condition what should Manu have done?
Answer: Pouring water to extinguish the fire due to oil is not a suitable action. It is because oil is lighter than water. So, water will settle down below the oil. In such a condition, sand or soil should be used.

They cut off the supply of air to the fire. Thus, fire can be controlled. But sand or soil will not be available at that place.

So, Manu should have switched off the flame ofthe burner and put a lid on the frying pan. By doing this, the contact between fuel and oxygen is cut, and the flame could go off.

Simple Friction Experiments For Class 8 Science CBSE Students Activity 1

Aim: To observe the opposing or friction force.

Material Required: A table, a book

Read And Learn More CBSE Class 8 Science Activities

Procedure:

1. Firstly, take a book and place it on the table.
2. Now, push the book gently towards the right. You will find that the book stops after covering some distance.
3. Now, push the book towards the left, and you will find that the book stops after covering some distance.

Conclusion: We can see that when the force is acting towards the left, the friction is towards the right, and when the force is acting towards the right, the friction is towards the left. Hence, we conclude that the force of friction always acts in a direction opposite to the direction of motion of an object

CBSE Fun Hands-On Friction Experiments For Grade 8 Students Activity 2

Aim: To show that the magnitude of friction is less over smooth surfaces with the help ofspring balance.

Material Required: A brick, a spring balance.

Procedure:

1. Firstly, tie a string around a brick and connect it to the hook of the spring balance.
2. Fully extend the other end of the spring balance by hand till the brick just begins to move.
3. Note the reading on the spring balance. It will give you the magnitude of the force of friction between the surface of the brick and the floor.
4. Now, wrap a piece of polythene around the brick and repeat the above steps to measure the magnitude ot the friction force.

Conclusion: We have concluded that the magnitude of friction is less, when we wrap the brick with a polythene. It means that smooth surfaces produce less friction.

CBSE Rolling Friction Demonstration Activity For Class 8 Science Activity 3

Aim: To observe the dependence of friction on the nature of surfaces.

Material Required: Wooden board, a pencil cell, a piece of cloth, some books, a table.

Procedure:

Firstly, set up an inclined plane on a smooth table by placing a wooden board supported by some books as shown.

Put a mark A on the inclined plane and let a pencil cell move down from this mark. Note the distance covered by the pencil cell on the table.

Now, put a piece of cloth over the table. Repeat the above steps again on the cloth spread over table. You will find that distance covered by the pencil cell is less than the distance covered in first case.

Again, repeat this activity by spreading a thin layer of sand over the table. You will find that the distance covered by the pencil cell is very small.

Conclusion: We have concluded that the distance covered by the pencil cell is different on different surfaces. Thus, the friction depends on the nature of the two surfaces in contact.

CBSE Class 8 Science Friction Activity Worksheet With Observations Activity 4

Aim: To show that rolling friction is less than the friction.

Material Required: A book. few pencils.

Procedure:

1. Firstly, take a few pencils of cylindrical shape and place them parallel to each other on a table.
2. Place a thick book over it.
3. Now, push the book gently. You will find that the pencils roll as the book moves.

Here, we find it easier to move the book in this way than to slide it.

Conclusion: We have concluded that the friction can be reduced by attaching wheels, to move an object. It is always easier to move an object by rolling as compare to sliding it.

CBSE Class 8 Science Chapter 9 Friction Fill In The Blanks

Question 1. Friction opposes the _________ between the surfaces in contact with each other.
Answer: Relative motion

Question 2. Friction depends on the _________ of surfaces.
Answer: Nature

Question 3. Friction produces _________.
Answer: Heat

Read And Learn More CBSE Class 8 Science Question And Answers

Question 4. Sprinkling of powder on the carrom board _________ friction.
Answer: Reduces

Question 5. Sliding friction is _________ than the static friction.
Answer: Less

Question 6. A spring balance is a device used for measuring the ________ acting on the object.
Answer: force

Question 7. On smooth surfaces, there are ________ number of irregularities. While on rough surfaces, there are an _______ number of irregularities.
Answer: Less, Large

Question 8. Friction can never be entirely ________.
Answer: Eliminated

Question 9. The soles of our shoes get worn out after a period of time. It is due to ________.
Answer: Friction

Question 10. ________ is produced by friction.
Answer: Heat

Question 11. Ball bearings reduce friction because they roll rather than ________.
Answer: Slide

Question 12. We pour a drop of oil on the hinge of the door to ________ friction.
Answer: Reduce

Question 13. Cars and speedboats are ________ to reduce drag.
Answer: Streamlined

CBSE Class 8 Science Chapter 9 Friction True Or False

Question 1. A fraction always works in the direction of the motion of the body.
Answer: False

Question 2. A soapy floor is slippery due to less friction.
Answer: True

Question 3. Friction increases with an increase in the smoothness of the surface.
Answer: False

Question 4. It is easier to roll the body over one another than to slide it.
Answer: True

Question 5. Friction enables vehicles to move on the ground.
Answer: True

Question 6. Fluid friction depends on the shape of an object placed in the fluid and the nature of the fluid.
Answer: True

Question 7. Athletes wear spikes to increase muscular force.
Answer: False

Question 8. A streamlined body shape helps in reducing drag.
Answer: True

Question 9. Frictional force does not depend on the nature of the
surfaces in contact
Answer: False

CBSE Class 8 Science Chapter 9 Friction Match The Columns

Question 1. Match Column 1 with those In Column 2

Answer: (a)-(2), (b)-(3), (c)-(5), (d)-(1), (e)-(4)

CBSE Class 8 Science Chapter 9 Friction Assertion-Reason Questions

The following questions consist of two statements: Assertion (A) and Reason (R). Answer these questions by selecting the appropriate option given below.

1. Both A and R are true, and R is the correct explanation of A.
2. Both A and R are true, but R is not the correct explanation of A.
3. A is true, but R is false.
4. A is false, but R is true.

Question 1.

Assertion (A): The  Force of friction is smaller on smooth surfaces than on rough surfaces.
Reason (R): Static friction is greater than the sliding friction.

Answer: 2. The  Force of friction is smaller on smooth surfaces than on rough surfaces because on smooth surfaces, the irregularities present are much less compared to rough surfaces.

Question 2.

Assertion (A): Lubricants increase the friction force.
Reason (R): Friction is a necessary evil.

Answer: 4. Lubricants are the materials that minimise the friction force. Friction has advantages as well as disadvantages. That’s why it is called a necessary evil.

Question 3.

Assertion (A) Birds can fly easily in the sky.
Reason (R) Streamlined body helps them in minimizing the friction.

Answer: 1. A body shape that offers a small resistance to the flow of fluid around it, is called streamlined shape. Birds have streamlined shape by nature. That’s why, they fly easily in the air.

Question 4.

Assertion (A) It is difficult to push or pull a heavier object than a lighter object.
Reason (R) Interlocking of irregularities is more prevalent between heavy object surfaces than light object surfaces

Answer: 1. The interlocking of irregularities is more between heavy object surfaces than light object surfaces. That’s why it is difficult to push or pull heavier objects.

The following questions consist of two statements -Assertion (A) and Reason (R). Answer these questions by selecting the appropriate option given below.

1. Both A and R are true, and R is the correct explanation of A.
2. Both A and R are true, but R is not the correct explanation of A.
3. A is true, but R is false.
4. A is false, but R is true.

Question 5.

Assertion (A): We often see that suitcases fitted with wheels are easy to pull.
Reason (R): Rolling friction is smaller than the static and sliding friction.

Answer: 1. Both A and R are true, and R is the correct explanation of A.

Question 6.

Assertion (A): Rocket and aeroplanes has a special body shape, i.e,. streamlined shape.
Reason (R): Streamlined shape helps an object reduce friction drag between the fluid and the object moving through it.

Answer: 1. Both A and R are true, and R is the correct explanation of A.

CBSE Class 8 Science Chapter 8 Force And Pressure Multiple Choice Questions

Question 1. In the figure, two boys, A and B, are shown applying force on a block. If the block moves towards the right, which one of the following statements is correct?

1. The magnitude of force applied by A is greater than that of B.
2. The magnitude of the force applied by A is smaller than that of B.
3. Net force on the block is towards A.
4. The magnitude of force applied by A is equal to that of B

Answer: 1. The Magnitude of force applied by A is greater than that of B.

Question 2. In the circuit shown in the figure, when the circuit is completed, the hammer strikes the gong. Which of the following forces is responsible for the movement of a hammer?

1. Gravitational force alone
2. Electrostatic force alone
3. Magnetic force alone
4. Frictional force alone

Answer: 3. Magnetic force alone

Question 3.

A brick is kept in three different ways on a table, as shown in the figure. The pressure exerted by the brick on the table will be

1. Maximum in position a
2. Maximum in position c
3. Maximum in position b
4. Equal in all cases

Answer: 1. Maximum in position a

Question 4. The figure shows a container filled with water. Which of the following statements is correct about the pressure of water?

1. Pressure at A > Pressure at B > Pressure at C
2. Pressure at A = Pressure at B = Pressure at C
3. Pressure at A < Pressure at B > Pressure at C
4. Pressure at A < Pressure at B < Pressure at C

Answer: 4. Pressure at A < Pressure at B < Pressure at C

Read And Learn More CBSE Class 8 Science Multiple Choice Questions

Question 5.

A water tank has four taps fixed at points A, B, C, and D as shown in the figure. The water will flow out at the same pressure from taps at

1. B and C
2. C and D
3. A and B
4. A and C

Answer: 1. B and C

Question 6. P, Q, and Rand S are four solid objects having the same mass. Which object is exerting the least pressure on the table?

1. P
2. Q
3. R
4. S

Answer: 2. Q

Question 7. Type of force where only attraction is found

1. Electrostatic force
2. Magnetic force
3. Gravitational force
4. Both (a) and (b)

Answer: 3. Gravitational force

Question 8. The wear and tear in the machine part is due to

1. Electrostatic force
2. Muscular force
3. Frictional force
4. Gravitational force

Answer: 3. Frictional force

Question 9. Like poles exert a force of

1. Attraction
2. Repulsion
3. Both 1 and 2
4. None of these

Answer: 4. None of these

Question 10. A block of mass 2 kg tied with a rope is going down under the force of gravity of 20 N.

How much force is required by the hand to stop the motion of the block?

1. 10 N
2. 20 N
3. 30 N
4. 40 N

Answer: 2. 20 N

Question 11. When a stone is rotated on a circular path uniformly, the effect of the force will be

1. Change in direction and magnitude of motion.
2. Change in shape of an object.
3. Change in direction of motion only.
4. Change in magnitude only.

Answer: 3. Change in direction of motion only.