Important Questions Class 8 Science Chapter 5: Exploring Forces

A force is a push or pull that can change the motion, direction or shape of an object.
Forces may act through contact or from a distance without physical contact.

Forces explain why bicycles slow down, magnets attract, charged objects pull paper pieces, objects fall, and some things float in water. Important Questions Class 8 Science Chapter 5 help students practise force, effects of force, contact forces, muscular force, friction, non-contact forces, magnetic force, electrostatic force, gravitational force, weight, spring balance, mass and weight, buoyant force, floating and sinking. The CBSE 2026 chapter explains these ideas through cycling, cardboard boxes, sliding objects, ring magnets, rubbed balloons, falling objects and bottles pushed into water.

Key Takeaways

• Force: A force is a push or pull resulting from interaction between two objects.
• SI Unit: The SI unit of force is newton, written with symbol N.
• Friction: Friction acts opposite to the direction of motion or attempted motion.
• Weight: Weight is the gravitational force with which Earth pulls an object.

Important Questions Class 8 Science Chapter 5 Structure 2026

Important Questions Class 8 Science Chapter 5 with Answers

Exploring Forces explains push, pull, motion change, contact forces, non-contact forces and buoyant force.
Students should name the force and state its direction wherever needed.
These exploring forces class 8 questions follow the NCERT 2026 chapter flow.

1. What does Important Questions Class 8 Science Chapter 5 mainly teach?

Important Questions Class 8 Science Chapter 5 mainly teach force, friction, muscular force, magnetic force, electrostatic force, gravity, weight and buoyancy. The chapter connects daily motion with different forces.

1. Force Skill: Identify push and pull.
2. Motion Skill: Explain speed, direction and shape changes.
3. Type Skill: Classify contact and non-contact forces.
4. Measurement Skill: Use spring balance for weight.
5. Final Result: Chapter 5 teaches how forces affect objects.

2. What is the name of Class 8 Science Chapter 5?

The name of Class 8 Science Chapter 5 is Exploring Forces. It explains contact forces, non-contact forces, weight and floating.

1. Chapter Number: 5.
2. Chapter Name: Exploring Forces.
3. Textbook: Curiosity.
4. Final Result: Chapter 5 is about forces and their effects.

3. Why did Sonali and Ragini pedal harder against the wind?

They pedalled harder because wind exerted an opposing force on them. Riding against wind needs extra muscular force.

1. Situation: Cycling against wind.
2. Opposing Force: Air resistance.
3. Action: Pedal harder.
4. Final Result: Wind can oppose bicycle motion.

Class 8 Science Chapter 5 Important Questions

Class 8 Science Chapter 5 important questions focus on identifying forces in everyday actions.
The chapter uses bicycles, balls, magnets, balloons, springs and water to explain force effects.
Students should write whether the force acts by contact or without contact.

4. What is a force?

A force is a push or pull on an object due to interaction with another object. It can change motion or shape.

1. Push Example: Pushing a cardboard box.
2. Pull Example: Pulling a drawer.
3. Interaction: At least two objects are involved.
4. Final Result: Force is a push or pull due to interaction.

5. What is the SI unit of force?

The SI unit of force is newton. Its symbol is N.

1. Unit Name: newton.
2. Symbol: N.
3. Correct Writing: 5 N.
4. Final Result: Force is measured in newton.

6. Why must at least two objects interact for force to act?

At least two objects must interact because force arises from interaction. One object applies force, and the other experiences it.

1. Example: Hand pushes table.
2. Object 1: Hand.
3. Object 2: Table.
4. Final Result: Force needs interaction between objects.

7. Does a force act on both interacting objects?

Yes, both interacting objects experience force from each other. When the interaction stops, the force also stops.

1. Hand and Table: Both exert forces.
2. Pushing Stops: Force stops.
3. Interaction: Required for force.
4. Final Result: Interacting objects exert forces on each other.

8. Does rest mean no force is acting on an object?

No, rest does not always mean no force is acting. Forces may balance one another.

1. Object at Rest: May have forces.
2. Balanced Forces: Cancel effects.
3. Motion: No change occurs.
4. Final Result: Balanced forces can keep an object at rest.

Force Class 8 Science Questions

Force class 8 science questions test push, pull and interaction.
Force can start motion, stop motion, change speed, change direction or deform objects.
A single action may produce more than one effect.

9. How can force move an object from rest?

Force can move an object from rest when a push or pull acts on it. A stationary box moves when pushed.

1. Initial State: Box at rest.
2. Applied Force: Push.
3. Effect: Box starts moving.
4. Final Result: Force can start motion.

10. How can force stop a moving object?

Force can stop a moving object by acting opposite to its motion. Brakes stop a moving bicycle.

1. Object: Moving bicycle.
2. Force Direction: Opposite motion.
3. Effect: Speed decreases to zero.
4. Final Result: Opposing force can stop motion.

11. How can force change direction of motion?

Force can change direction when it acts sideways or at an angle to motion. A bat changes the direction of a moving ball.

1. Object: Moving ball.
2. Force: Bat push.
3. Effect: Direction changes.
4. Final Result: Force can change motion direction.

12. How can force change shape?

Force can change shape when it compresses, stretches or bends an object. Pressing an inflated balloon changes its shape.

1. Object: Inflated balloon.
2. Force: Push.
3. Effect: Shape changes.
4. Final Result: Force can deform objects.

13. Can one force produce several effects?

Yes, one force can produce several effects. Kicking a football can start motion and change direction.

1. Action: Kick a football.
2. Effect 1: Starts motion.
3. Effect 2: Changes speed and direction.
4. Final Result: A force may cause multiple effects.

Effects of Force Class 8 Questions

Effects of force class 8 questions explain how objects respond to force.
A force may change speed, direction, shape or all three.
No such change occurs without the action of force.

14. List the main effects of force.

The main effects of force are motion from rest, change in speed, change in direction and change in shape. A force can cause one or more effects.

1. Motion: Start or stop.
2. Speed: Increase or decrease.
3. Direction: Change path.
4. Shape: Stretch, compress or bend.
5. Final Result: Force changes motion or shape.

15. What force acts when brakes are applied on a bicycle?

Friction acts when brakes are applied on a bicycle. It slows down the moving bicycle.

1. Action: Apply brakes.
2. Force: Friction.
3. Effect: Speed decreases.
4. Final Result: Brakes use friction to stop a bicycle.

16. What effect of force is seen while rolling a chapati?

Rolling a chapati shows change in shape due to force. The rolling pin presses and spreads the dough.

1. Object: Dough.
2. Force: Pressure from rolling pin.
3. Effect: Dough becomes flatter.
4. Final Result: Force changes the shape of dough.

17. What effect of force is seen when an autorickshaw turns?

Turning an autorickshaw shows change in direction due to force. The handle changes the motion direction.

1. Object: Moving autorickshaw.
2. Action: Turn handle.
3. Effect: Direction changes.
4. Final Result: Force changes direction of motion.

18. Why does a bicycle move faster when pedalled harder?

A bicycle moves faster because stronger muscular force acts through the pedals. Greater push can increase speed.

1. Action: Pedalling.
2. Force: Muscular force.
3. Effect: Speed increases.
4. Final Result: Greater pedalling force increases bicycle speed.

Contact Forces Class 8 Questions

Contact forces class 8 questions explain forces that need physical contact.
Contact may be direct through hands or indirect through a stick, rope or tool.
Muscular force and friction are contact forces.

19. What are contact forces?

Contact forces are forces that act only when objects are in physical contact. They cannot act from a distance.

1. Direct Contact: Hand pushes a box.
2. Indirect Contact: Rope pulls an object.
3. Examples: Muscular force and friction.
4. Final Result: Contact forces need touching surfaces or links.

20. Why is muscular force a contact force?

Muscular force is a contact force because it acts when muscles apply force through contact. We push, pull, lift or carry objects using muscles.

1. Source: Muscles.
2. Contact: Body touches object.
3. Example: Lifting a school bag.
4. Final Result: Muscular force needs contact.

21. Why is friction a contact force?

Friction is a contact force because it arises between two surfaces in contact. It opposes motion or attempted motion.

1. Surfaces: Object and floor.
2. Contact: Required.
3. Direction: Opposite motion.
4. Final Result: Friction acts only between contact surfaces.

22. Can contact force act through a rope?

Yes, contact force can act through a rope. Pulling a rope applies force indirectly on an object.

1. Object: Rope.
2. Action: Pull.
3. Force Transfer: Rope pulls another object.
4. Final Result: Ropes can transmit contact force.

Muscular Force Class 8 Questions

Muscular force class 8 questions explain forces produced by muscles.
Humans and animals use muscular force for movement, lifting, pulling, chewing and survival.
Muscular force occurs when muscles contract and elongate.

23. What is muscular force?

Muscular force is the force produced by the action of muscles. It is used in walking, running, lifting, pushing and jumping.

1. Source: Muscles.
2. Action: Contract and elongate.
3. Example: Lifting a bag.
4. Final Result: Muscular force comes from muscles.

24. Give examples of muscular force in humans.

Examples include walking, running, lifting, chewing food and pushing a door. These actions use muscles.

1. Movement: Walking and running.
2. Work: Lifting a box.
3. Body Function: Chewing food.
4. Final Result: Humans use muscular force in daily activities.

25. How do animals use muscular force?

Animals use muscular force for walking, running, flying, swimming, pulling loads and survival. Fish use muscles to swim.

1. Birds: Fly using muscles.
2. Fish: Swim using muscles.
3. Bullocks: Pull carts using muscles.
4. Final Result: Animals use muscular force for movement and work.

26. How does muscular force help inside the body?

Muscular force helps chew food, move food through the alimentary canal and circulate blood. Heart muscles expand and contract.

1. Mouth: Chewing.
2. Food Pipe: Pushing food down.
3. Heart: Pumping blood.
4. Final Result: Muscular force supports body functions.

Friction Class 8 Questions

Friction class 8 questions explain why moving objects slow down.
Friction acts opposite to motion or attempted motion.
It depends on the nature of the surfaces in contact.

27. What is friction?

Friction is the force that acts when an object moves or tries to move over another surface. It opposes motion.

1. Contact: Two surfaces touch.
2. Direction: Opposite motion.
3. Example: Sliding box stops.
4. Final Result: Friction opposes motion between surfaces.

28. Why does a rolling ball stop on flat ground?

A rolling ball stops because friction acts between the ball and ground. Air also offers resistance.

1. Object: Rolling ball.
2. Surface Force: Friction.
3. Effect: Speed decreases.
4. Final Result: Friction slows the rolling ball.

29. Why does a bicycle stop when we stop pedalling?

A bicycle stops because friction and air resistance oppose its motion. These forces reduce its speed.

1. Road Contact: Tyres experience friction.
2. Air: Opposes motion.
3. Effect: Bicycle slows down.
4. Final Result: Opposing forces bring the bicycle to rest.

30. Why is friction greater on rough surfaces?

Friction is greater on rough surfaces because surface irregularities lock more strongly. This opposes motion more.

1. Rough Surface: More irregularities.
2. Locking: Stronger between surfaces.
3. Effect: More friction.
4. Final Result: Rough surfaces produce greater friction.

31. Why does an object slide farther on smooth surfaces?

An object slides farther because smooth surfaces create less friction. Less opposing force allows longer motion.

1. Smooth Surface: Fewer strong irregularities.
2. Friction: Lower.
3. Distance: Greater before stopping.
4. Final Result: Low friction allows longer sliding.

32. Why do we slip on wet or polished floors?

We slip because wet or polished surfaces reduce friction. The feet do not grip the floor properly.

1. Surface: Wet or polished.
2. Friction: Reduced.
3. Effect: Foot slips.
4. Final Result: Low friction causes slipping.

33. Is friction always harmful?

No, friction is not always harmful. It helps us walk, write, grip objects and apply brakes.

1. Walking: Needs friction.
2. Writing: Pencil needs friction on paper.
3. Braking: Uses friction.
4. Final Result: Friction is necessary in many activities.

34. How do air and water exert friction?

Air and water exert friction on objects moving through them. This friction opposes motion.

1. Air: Opposes aeroplanes and trains.
2. Water: Opposes boats and ships.
3. Design: Shapes reduce friction.
4. Final Result: Fluids also exert friction.

Non Contact Forces Class 8 Questions

Non contact forces class 8 questions explain forces acting from a distance.
Objects need not touch each other for these forces to act.
Magnetic force, electrostatic force and gravitational force are non-contact forces.

35. What are non-contact forces?

Non-contact forces are forces that act without physical contact between objects. They act from a distance.

1. Magnetic Force: Acts between magnets.
2. Electrostatic Force: Acts between charged objects.
3. Gravitational Force: Earth pulls objects.
4. Final Result: Non-contact forces do not need touching.

36. Why is gravitational force a non-contact force?

Gravitational force is non-contact because Earth pulls objects without touching them. Falling objects show this force.

1. Object: Falling fruit.
2. Source: Earth.
3. Contact: Not needed.
4. Final Result: Gravity acts from a distance.

37. Why is magnetic force a non-contact force?

Magnetic force is non-contact because a magnet can attract or repel without touching another magnet or magnetic material.

1. Magnet: Exerts force.
2. Target: Magnet or magnetic material.
3. Contact: Not required.
4. Final Result: Magnetic force acts without contact.

38. Why is electrostatic force a non-contact force?

Electrostatic force is non-contact because a charged object can attract another object from a distance. A charged straw attracts paper pieces.

1. Charged Object: Rubbed straw.
2. Object: Paper pieces.
3. Contact: Not needed at first.
4. Final Result: Electrostatic force acts from a distance.

Magnetic Force Class 8 Questions

Magnetic force class 8 questions explain attraction and repulsion by magnets.
A magnet can attract magnetic materials and interact with another magnet.
Like poles repel, and unlike poles attract.

39. What is magnetic force?

Magnetic force is the force exerted by a magnet on another magnet or magnetic material. It can act without contact.

1. Magnet-Material: Attraction.
2. Magnet-Magnet: Attraction or repulsion.
3. Force Type: Non-contact force.
4. Final Result: Magnetic force acts between magnets and magnetic materials.

40. What happens when like poles of two magnets face each other?

Like poles repel each other. North-North and South-South pole pairs push away.

1. Like Pair: N-N or S-S.
2. Interaction: Repulsion.
3. Example: Floating ring magnet setup.
4. Final Result: Like magnetic poles repel.

41. What happens when unlike poles of two magnets face each other?

Unlike poles attract each other. North-South pole pairs pull towards each other.

1. Unlike Pair: N-S.
2. Interaction: Attraction.
3. Effect: Magnets move closer.
4. Final Result: Unlike magnetic poles attract.

42. Why can a ring magnet float above another ring magnet?

A ring magnet can float when like poles face each other. Magnetic repulsion supports the upper magnet.

1. Lower Magnet: One pole faces up.
2. Upper Magnet: Same pole faces down.
3. Force: Upward repulsion.
4. Final Result: Like-pole repulsion can make the magnet float.

43. Why does a compass needle point north?

A compass needle points north because it is a magnet that responds to Earth’s magnetic effect. Magnetic force aligns it.

1. Compass Needle: Small magnet.
2. Earth: Acts like a magnet.
3. Effect: Needle aligns north-south.
4. Final Result: Magnetic force aligns the compass needle.

Electrostatic Force Class 8 Questions

Electrostatic force class 8 questions explain forces due to static charges.
Rubbing certain materials transfers charge to their surfaces.
Like charges repel, and unlike charges attract.

44. What is electrostatic force?

Electrostatic force is the force exerted by a charged body on another charged or uncharged body. It acts without contact.

1. Charged Body: Rubbed plastic scale.
2. Object: Paper pieces or charged balloon.
3. Force Type: Non-contact force.
4. Final Result: Electrostatic force arises due to charges.

45. What are static charges?

Static charges are electrical charges that build up on object surfaces after rubbing. They do not move by themselves.

1. Action: Rubbing materials.
2. Location: Object surface.
3. Example: Rubbed straw attracts paper.
4. Final Result: Static charges stay on surfaces.

46. Why does a rubbed plastic scale attract paper pieces?

A rubbed plastic scale attracts paper pieces because it becomes charged. The charged scale exerts electrostatic force on paper.

1. Scale: Rubbed with polythene.
2. Charge: Builds up on scale.
3. Effect: Paper pieces move towards scale.
4. Final Result: Charged scale attracts paper pieces.

47. What happens when two rubbed balloons are brought close?

Two rubbed balloons repel each other. They acquire similar charges after being rubbed with the same woollen cloth.

1. Objects: Two balloons.
2. Charge Type: Similar charges.
3. Effect: Repulsion.
4. Final Result: Like charges repel.

48. Why does a rubbed balloon attract the woollen cloth?

A rubbed balloon attracts the woollen cloth because they acquire opposite charges. Unlike charges attract each other.

1. Balloon: Gets one kind of charge.
2. Woollen Cloth: Gets opposite charge.
3. Interaction: Attraction.
4. Final Result: Unlike charges attract.

49. What are the two kinds of static charges?

The two kinds of static charges are positive and negative. Similar charges repel, and unlike charges attract.

1. Charge Type 1: Positive.
2. Charge Type 2: Negative.
3. Rule: Like repel, unlike attract.
4. Final Result: Static charges are positive or negative.

Gravitational Force Class 8 Questions

Gravitational force class 8 questions explain why objects fall towards Earth.
Earth pulls every object towards itself.
Gravitational force is always attractive.

50. What is gravitational force?

Gravitational force is the force with which Earth attracts objects towards itself. It is also called gravity.

1. Source: Earth.
2. Direction: Towards Earth.
3. Nature: Always attractive.
4. Final Result: Gravity pulls objects towards Earth.

51. Why does a ball thrown upward come back down?

A ball thrown upward comes back down because Earth pulls it through gravitational force. Gravity acts downward throughout.

1. Upward Motion: Gravity slows the ball.
2. Top Position: Ball stops momentarily.
3. Downward Motion: Gravity increases speed.
4. Final Result: Gravity brings the ball back to Earth.

52. What force acts on a ball during upward motion?

Gravity acts downward during upward motion. Friction due to air also acts opposite to motion.

1. Gravity: Downward.
2. Air Friction: Downward during upward motion.
3. Effect: Ball slows down.
4. Final Result: Downward forces reduce upward speed.

53. What force acts on a ball during downward motion?

Gravity acts downward during downward motion, while air friction acts upward. Gravity makes the ball speed up downward.

1. Gravity: Downward.
2. Air Friction: Upward.
3. Effect: Ball falls faster until resistance matters.
4. Final Result: Gravity pulls the falling ball downward.

54. What force acts at the topmost position of a thrown ball?

Gravity acts downward even at the topmost position. The ball is momentarily at rest there.

1. Position: Topmost point.
2. Speed: Momentarily zero.
3. Force: Gravity downward.
4. Final Result: Gravity acts even when speed is momentarily zero.

55. Why is gravitational force called non-contact force?

Gravity is called non-contact force because Earth pulls objects without touching them. A falling fruit shows this force.

1. Earth: Pulls the fruit.
2. Fruit: Falls downward.
3. Contact: Not required.
4. Final Result: Gravity acts without physical contact.

Weight and Mass Class 8 Questions

Weight and mass class 8 questions explain a common scientific difference.
Mass is the amount of matter in an object.
Weight is the gravitational force acting on the object.

56. What is weight?

Weight is the force with which Earth pulls an object towards itself. It is measured in newton.

1. Force: Gravitational pull.
2. Source: Earth.
3. SI Unit: N.
4. Final Result: Weight is gravitational force on an object.

57. What is mass?

Mass is the amount of matter in an object. It is measured in gram or kilogram.

1. Quantity: Matter present.
2. Units: g and kg.
3. Value: Remains same everywhere.
4. Final Result: Mass measures amount of matter.

58. What is the difference between mass and weight?

Mass is the amount of matter, while weight is gravitational force. Mass remains unchanged, but weight can vary from place to place.

1. Mass Unit: kg.
2. Weight Unit: N.
3. Moon Example: Same mass, lower weight.
4. Final Result: Mass is constant, weight depends on gravity.

59. Why does weight change on the Moon?

Weight changes on the Moon because the Moon’s gravitational pull is weaker than Earth’s. The mass remains unchanged.

1. Earth Weight: Greater.
2. Moon Weight: About one-sixth of Earth weight.
3. Mass: Same value.
4. Final Result: Lower lunar gravity reduces weight.

60. What is the weight of a 1 kg object on Earth and Moon?

A 1 kg object weighs about 10 N on Earth and 1.6 N on the Moon. Its mass remains 1 kg.

1. Mass: 1 kg.
2. Earth Weight: 10 N.
3. Moon Weight: 1.6 N.
4. Final Result: Same mass has different weight on Earth and Moon.

61. Why is saying “weight is 10 kg” scientifically incorrect?

It is scientifically incorrect because kilogram is a unit of mass, not weight. Weight should be written in newton.

1. Mass Unit: kg.
2. Weight Unit: N.
3. Correct Scientific Use: Mass is 10 kg.
4. Final Result: Weight must be measured in newton.

Spring Balance Class 8 Questions

Spring balance class 8 questions explain how weight is measured.
A spring stretches when an object is hung from it.
The amount of stretch gives the weight of the object.

62. What is a spring balance?

A spring balance is a device used to measure weight or force. It has a spring and a scale marked in newton.

1. Main Part: Spring.
2. Hook: Holds object.
3. Scale: Shows force in N.
4. Final Result: Spring balance measures weight.

63. How does a spring balance measure weight?

A spring balance measures weight by the stretch of its spring. Heavier objects stretch the spring more.

1. Object: Hung from hook.
2. Gravity: Pulls object downward.
3. Spring: Stretches.
4. Final Result: Spring stretch shows object weight.

64. Why should heavy objects not be hung from a small spring balance?

Heavy objects should not be hung because they can exceed the range and damage the spring balance. The object must stay within the maximum reading.

1. Instrument Range: Limited.
2. Heavy Object: May overstretch spring.
3. Risk: Damage.
4. Final Result: Use objects within spring balance range.

65. A spring balance has 5 small divisions between 0 N and 1 N. What is the least count?

The least count is 0.2 N. Divide 1 N by 5 divisions.

1. Big Mark Difference: 1 N.
2. Number of Divisions: 5.
3. Calculation: 1 ÷ 5 = 0.2 N.
4. Final Result: Least count = 0.2 N.

66. Why should the scale be read carefully on a spring balance?

The scale should be read carefully because each spring balance may have a different range and least count. Wrong reading gives wrong weight.

1. Range: Maximum measurable value.
2. Least Count: Smallest reading.
3. Reading: Must align with pointer.
4. Final Result: Careful reading gives accurate weight.

Buoyant Force Class 8 Questions

Buoyant force class 8 questions explain the upward push of liquids.
When an object is placed in a liquid, gravity pulls it downward.
The liquid pushes it upward through buoyant force.

67. What is buoyant force?

Buoyant force is the upward force applied by a liquid on an object placed in it. It is also called upthrust.

1. Medium: Liquid.
2. Direction: Upward.
3. Other Name: Upthrust.
4. Final Result: Buoyant force pushes objects upward in liquids.

68. Why does an empty bottle bounce up when pushed into water?

The empty bottle bounces up because water exerts upward buoyant force on it. The upward force makes it rise.

1. Object: Empty closed bottle.
2. Liquid: Water.
3. Force: Upward buoyant force.
4. Final Result: Water pushes the bottle upward.

69. What forces act on an object placed in water?

Gravity acts downward, and buoyant force acts upward. Their relative sizes decide floating or sinking.

1. Downward Force: Weight.
2. Upward Force: Buoyant force.
3. Result: Sink or float.
4. Final Result: Two opposite forces act in water.

70. When does an object sink in water?

An object sinks when gravitational force is greater than buoyant force. It then moves to the bottom.

1. Weight: Greater than upthrust.
2. Net Force: Downward.
3. Example: Coin in water.
4. Final Result: Greater weight makes an object sink.

71. When does an object float in water?

An object floats when buoyant force balances its weight. The object stays on the surface or partly immersed.

1. Weight: Balanced by upthrust.
2. Net Force: Zero.
3. Example: Wooden block.
4. Final Result: Balanced forces make an object float.

72. Why does a mug feel lighter inside water?

A mug feels lighter inside water because water applies upward buoyant force. This reduces the effective pull felt by the hand.

1. Mug: Inside water.
2. Buoyant Force: Acts upward.
3. Feeling: Mug feels lighter.
4. Final Result: Upthrust reduces apparent weight in water.

73. What is Archimedes’ principle?

Archimedes’ principle states that an immersed object experiences an upward force equal to the weight of the liquid displaced. It applies to full or partial immersion.

1. Object: Immersed in liquid.
2. Liquid Displaced: Has weight.
3. Upward Force: Equal to displaced liquid’s weight.
4. Final Result: Buoyant force equals weight of displaced liquid.

Floating and Sinking Class 8 Questions

Floating and sinking class 8 questions explain why some objects stay on water and others go down.
The outcome depends on weight and buoyant force.
Liquid density also affects buoyant force.

74. Why does a coin sink but a wooden block float?

A coin sinks because its weight is greater than the buoyant force. A wooden block floats because buoyant force balances its weight.

1. Coin: Greater downward force.
2. Wooden Block: Upthrust balances weight.
3. Result: Coin sinks, wood floats.
4. Final Result: Floating depends on weight and buoyant force.

75. Why do some rocks float on water?

Some rocks float because they have many air pockets and are less dense than water. Pumice is one such rock.

1. Rock: Pumice.
2. Formation: Volcanic lava traps gas bubbles.
3. Property: Less dense than water.
4. Final Result: Pumice can float due to air pockets.

76. Why does liquid density affect buoyant force?

Liquid density affects buoyant force because denser liquids can provide greater upthrust for the same immersed object. This affects floating.

1. Liquid: Applies upward force.
2. Density: Changes upthrust.
3. Result: Floating becomes easier in denser liquids.
4. Final Result: Buoyant force depends on liquid density.

77. Three same-sized objects dip to different depths in water. Which object has greatest weight?

The object that dips deepest has the greatest weight. Greater weight needs greater displaced water to balance it.

1. Same Size: Same maximum volume.
2. More Immersion: More displaced water.
3. Greatest Depth: Greatest weight.
4. Final Result: Deepest-floating object has greatest weight among floaters.

NCERT Class 8 Science Chapter 5 Questions

NCERT Class 8 Science Chapter 5 questions test force matching, friction, charges, gravity, weight and buoyancy.
Students should mention whether the force is contact or non-contact.
These NCERT Class 8 Science Chapter 5 questions follow the 2026 exercise pattern.

78. Match muscular force with the correct example.

Muscular force matches with a child lifting a school bag. The child uses muscles to lift the bag.

1. Force Type: Muscular force.
2. Example: Lifting a school bag.
3. Category: Contact force.
4. Final Result: Muscular force matches lifting a school bag.

79. Match magnetic force with the correct example.

Magnetic force matches with a compass needle pointing North. The compass needle responds to magnetic force.

1. Force Type: Magnetic force.
2. Example: Compass needle.
3. Category: Non-contact force.
4. Final Result: Magnetic force matches compass needle direction.

80. Match frictional force with the correct example.

Frictional force matches with a cricket ball stopping before the boundary line. Friction slows the moving ball.

1. Force Type: Frictional force.
2. Example: Cricket ball stopping.
3. Direction: Opposite motion.
4. Final Result: Friction matches the stopping ball.

81. Match gravitational force with the correct example.

Gravitational force matches with a fruit falling from a tree. Earth pulls the fruit downward.

1. Force Type: Gravitational force.
2. Example: Falling fruit.
3. Category: Non-contact force.
4. Final Result: Gravity matches falling fruit.

82. Match electrostatic force with the correct example.

Electrostatic force matches with a balloon rubbed on woollen cloth attracting hair strands. Static charge causes attraction.

1. Force Type: Electrostatic force.
2. Example: Rubbed balloon attracting hair.
3. Category: Non-contact force.
4. Final Result: Electrostatic force matches charged balloon attraction.

83. Is force always required to change the speed of motion?

Yes, force is required to change speed. A moving object speeds up or slows down only when force acts.

1. Speed Increase: Needs force.
2. Speed Decrease: Needs opposing force.
3. Example: Bicycle brakes.
4. Final Result: Force changes speed.

84. Does friction increase the speed of a rolling ball on flat ground?

No, friction does not increase the speed of a rolling ball. It slows the ball down.

1. Force: Friction.
2. Direction: Opposite motion.
3. Effect: Speed decreases.
4. Final Result: Friction reduces the speed of a rolling ball.

85. Is there no force between two charged objects at a small distance?

No, that statement is false. Charged objects exert electrostatic force even without touching.

1. Objects: Charged bodies.
2. Force: Electrostatic force.
3. Contact: Not required.
4. Final Result: Charged objects can exert force from a distance.

86. What happens when two balloons rubbed with woollen cloth are brought near each other?

The balloons repel each other because both acquire similar charges. Like charges repel.

1. Action: Rub both balloons with woollen cloth.
2. Charge: Similar charge on both.
3. Effect: Repulsion.
4. Final Result: Similarly charged balloons repel.

87. Why does a ball stop before point A on a horizontal surface?

A ball can stop before point A if friction is increased. A rougher surface will make it stop earlier.

1. Change: Use rough surface.
2. Friction: Increases.
3. Stopping Distance: Decreases.
4. Final Result: More friction makes the ball stop before A.

88. How can a ball cross point A before stopping?

A ball can cross point A if friction is reduced. A smoother surface will let it travel farther.

1. Change: Use smoother surface.
2. Friction: Decreases.
3. Stopping Distance: Increases.
4. Final Result: Less friction lets the ball cross A.

89. Is force being applied to an object in non-uniform motion?

Yes, force is acting on an object in non-uniform motion. Non-uniform motion means speed or direction changes.

1. Non-uniform Motion: Motion changes.
2. Change: Speed or direction changes.
3. Cause: Force.
4. Final Result: Non-uniform motion indicates force.

90. Why does weight become one-sixth on the Moon?

Weight becomes one-sixth because the Moon’s gravitational force is much weaker than Earth’s. Mass does not become one-sixth.

1. Weight: Depends on gravity.
2. Moon Gravity: Weaker.
3. Mass: Remains same.
4. Final Result: Only weight changes on the Moon.

Class 8 Science Chapter 5 Questions and Answers

Class 8 Science Chapter 5 questions and answers should use force names and directions.
Students should avoid writing kilogram as the unit of weight in scientific answers.
These answers support quick revision for school tests.

91. Why is it harder to pedal uphill?

It is harder to pedal uphill because gravity pulls the bicycle and rider downward along the slope. More muscular force is needed.

1. Slope: Uphill.
2. Opposing Effect: Gravity.
3. Action Needed: Stronger pedalling.
4. Final Result: Uphill cycling needs more muscular force.

92. Why do bicycles move fast downhill without pedalling?

Bicycles move fast downhill because gravity pulls them down the slope. Their speed increases even without pedalling.

1. Slope: Downhill.
2. Force: Gravity.
3. Effect: Speed increases.
4. Final Result: Gravity accelerates bicycles downhill.

93. Why do rough roads make cycling harder?

Rough roads make cycling harder because friction is greater on rough surfaces. More muscular force is needed to keep moving.

1. Surface: Rough road.
2. Friction: More.
3. Effect: Cycling becomes harder.
4. Final Result: Rough surfaces increase friction.

94. Why do high-speed trains have special shapes?

High-speed trains have special shapes to reduce air friction. This helps them move faster and more efficiently.

1. Medium: Air.
2. Force: Fluid friction.
3. Design: Smooth shape.
4. Final Result: Streamlined shapes reduce air resistance.

95. Why is gravitational force always attractive?

Gravitational force is always attractive because it pulls objects towards each other. Earth pulls all objects towards itself.

1. Earth: Pulls objects.
2. Direction: Towards Earth.
3. No Repulsion: Gravity does not repel.
4. Final Result: Gravity is always attractive.

Class 8 Science Chapter List