Change speed, direction, or shape

Which statement is TRUE?

Forces arise due to interactions between at least two objects

A single isolated object can experience force without interaction

Force is not needed to change direction

Which example uses muscular force?

Charged balloon repelling another

Friction between two solids arises chiefly due to:

Microscopic irregularities interlocking

Which statement about friction is CORRECT?

It is always useful and never harmful

It increases speed automatically

Magnetic force can be observed when:

Two magnets attract or repel without touching

Ring magnets placed with like poles facing show:

Repulsion and ‘floating’ separation

A beam balance compares:

Weights to find mass equivalently

Ships float although made of steel because their average density:

Is less than water due to hollow design

Two equal-sized blocks, wood and iron, placed in water—wood floats and iron sinks. The correct reason is:

Wood’s density is lower than water, iron’s is higher

NCERT Solutions Class 8 Science - Curiosity Chapter 5 – Exploring Forces

Name: Exploring Forces – Class 8 Science - Curiosity
Uploaded: 2026-05-31
Description: A force is a push or pull that can move, stop, or change the shape or direction of an object. Forces can be contact (like muscular force and friction) or non-contact (like magnetic, electrostatic, and gravitational forces). The chapter also explains weight, buoyancy, and why some objects float or sink in liquids.

Class 8 Science - Curiosity

Last Updated: 31 May 2026

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Chapter Introduction

A force is a push or pull that can move, stop, or change the shape or direction of an object. Forces can be contact (like muscular force and friction) or non-contact (like magnetic, electrostatic, and gravitational forces). The chapter also explains weight, buoyancy, and why some objects float or sink in liquids.

हिंदी में (Hindi)

बल किसी वस्तु को धकेलने या खींचने की क्रिया है, जो उसकी गति, दिशा या आकार बदल सकती है। बल दो प्रकार के होते हैं—स्पर्श बल (जैसे पेशीय बल और घर्षण) और अस्पर्श बल (जैसे चुंबकीय, विद्युतस्थैतिक और गुरुत्वीय बल)। अध्याय में भार, उत्प्लावन और वस्तुओं के तैरने या डूबने के कारण भी समझाए गए हैं।

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Important Points

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Practice MCQ Questions (67 questions)

Q1. What is a force in science?

Q2. Which action best shows a PUSH being applied?

Q3. Which action best shows a PULL being applied?

Q4. Which unit is used to measure force in SI?

Q5. In Activity 5.1, moving a box in many ways illustrates that:

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Tough Words (Glossary)

landscapes

Meaning: wide views of natural scenery like hills, fields, rivers

अर्थ: प्राकृतिक दृश्य/परिदृश्य

"We cycled to see the beautiful landscapes near our village."

tyres

Meaning: rubber covers around wheels filled with air

अर्थ: टायर (पहियों के रबर आवरण)

"We pumped air into the bicycle tyres before riding."

thunder

Meaning: a loud rumbling sound after lightning

अर्थ: बिजली गरजने की आवाज़ (गरजन)

"We heard thunder in the distance."

lightning

Meaning: a bright flash of electricity in the sky during a storm

अर्थ: बिजली की चमक

"Flashes of lightning lit up the sky."

herd

Meaning: a group of animals of the same kind

अर्थ: झुंड

"They passed a herd of sheep on the way back."

slope

Meaning: a surface that is not flat and goes up or down

अर्थ: ढलान

"The bicycles sped up while going down the slope."

thrilling

Meaning: very exciting and full of feeling

अर्थ: रोमांचक

"Riding downhill without pedalling felt thrilling."

pedal

Meaning: to push the foot levers of a cycle

अर्थ: पैडल चलाना

"You must pedal harder against the wind."

direction

Meaning: the course along which something moves or points

अर्थ: दिशा

"They turned the handle to change direction."

realise

Meaning: to understand or become aware of

अर्थ: समझना/अहसास होना

"They realised the cycles were moving faster downhill."

force

Meaning: a push or a pull that can change motion or shape

अर्थ: बल

"A force can change the speed of an object."

friction

Meaning: a force that opposes motion between two surfaces in contact

अर्थ: घर्षण

"Friction made it hard to pedal on the rough road."

contact

Meaning: touching; being in physical connection

अर्थ: संपर्क

"Pushing a table is a contact force."

non‑contact

Meaning: acting from a distance without touching

अर्थ: असंर्पक (बिना छुए)

"Gravity is a non‑contact force."

magnetic

Meaning: related to magnets or magnetism

अर्थ: चुंबकीय

"A magnet exerts a magnetic force on iron."

electrostatic

Meaning: related to electric charges at rest

अर्थ: स्थिर वैद्युत (इलेक्ट्रोस्टैटिक)

"A rubbed balloon shows electrostatic force."

gravitational

Meaning: related to the pull between masses (like Earth’s pull)

अर्थ: गुरुत्वीय/गुरुत्वाकर्षण संबंधी

"Objects fall due to gravitational force."

repel

Meaning: to push away

अर्थ: परस्पर दूर करना/प्रतिरोध करना

"Like magnetic poles repel each other."

attract

Meaning: to pull toward

अर्थ: आकर्षित करना

"Opposite charges attract."

unit (newton)

Meaning: standard quantity for measuring force; newton (N) is SI unit

अर्थ: माप की इकाई; बल की SI इकाई न्यूटन (N)

"Weight is measured in the unit newton."

interaction

Meaning: a mutual action or influence between objects

अर्थ: परस्पर क्रिया/संक्रिया

"Force appears when there is an interaction."

muscular

Meaning: related to muscles

अर्थ: मांसपेशीय

"Walking uses muscular force."

irregularities

Meaning: small bumps and pits on surfaces

अर्थ: अनियमित उभार/असमानताएँ

"Friction is caused by surface irregularities."

oppose

Meaning: to act against; to resist

अर्थ: विरोध करना

"Friction opposes motion."

surface

Meaning: the outside layer of an object

अर्थ: सतह

"The object slid across the smooth surface."

vertical

Meaning: straight up and down

अर्थ: लंबवत

"The ball moved in a vertical path."

upthrust

Meaning: the upward push by a liquid on an object

अर्थ: उत्थापन बल/ऊर्ध्व बल

"A bottle feels a strong upthrust in water."

buoyant

Meaning: able to float; related to upward force in fluids

अर्थ: उत्प्लावक/तैरने योग्य

"A wooden block is buoyant in water."

density

Meaning: mass per unit volume; how tightly matter is packed

अर्थ: घनत्व

"Buoyant force depends on the density of liquid."

principle

Meaning: a basic law explaining how something works

अर्थ: सिद्धांत

"Archimedes’ principle explains floating."

Archimedes

Meaning: a Greek scientist known for work on buoyancy

अर्थ: आर्किमिडीज़ (ग्रीक वैज्ञानिक)

"Archimedes studied floating objects."

gravity

Meaning: the pull of Earth (or any mass) on objects

अर्थ: गुरुत्वाकर्षण

"Gravity pulls objects toward Earth."

weight

Meaning: the force with which Earth pulls an object

अर्थ: भार (पृथ्वी का खिंचाव)

"Weight is measured in newtons."

mass

Meaning: the amount of matter in an object

अर्थ: द्रव्यमान

"Mass stays the same everywhere."

spring balance

Meaning: a device with a spring to measure force/weight

अर्थ: स्प्रिंग तुला/स्प्रिंग बैलेंस

"We used a spring balance to measure weight."

range (instrument)

Meaning: the maximum and minimum values an instrument can measure

अर्थ: माप सीमा

"Check the range before using the balance."

division (scale)

Meaning: the small marked steps on a measuring scale

अर्थ: भाग/खंड (पैमाने पर)

"One small division equals 0.2 N."

balanced forces

Meaning: forces that cancel each other; no change in motion

अर्थ: संतुलित बल

"A resting box has balanced forces on it."

rough

Meaning: not smooth; uneven

अर्थ: खुरदुरा/असमान

"The rough track increased friction."

smooth

Meaning: even and flat; not rough

अर्थ: चिकना

"Objects slide farther on a smooth floor."

accelerate

Meaning: to increase speed

अर्थ: वेग बढ़ना/त्वरण पाना

"A force can accelerate a bicycle."

decelerate

Meaning: to decrease speed

अर्थ: वेग घटाना/धीमा होना

"Brakes decelerate the bike."

steer

Meaning: to control the direction of movement

अर्थ: हांकना/दिशा देना

"He used the handle to steer left."

compass (magnetic)

Meaning: a device with a magnetized needle showing direction

अर्थ: दिशासूचक (चुंबकीय)

"A compass deflects near a magnet."

deflect

Meaning: to change direction or bend aside

अर्थ: मोड़ लेना/विचलित होना

"The needle deflects when current flows."

charges (positive/negative)

Meaning: types of electric property that cause attraction/repulsion

अर्थ: आवेश (धनात्मक/ऋणात्मक)

"Like charges repel, unlike charges attract."

static

Meaning: not moving; at rest

अर्थ: स्थिर

"Static charges build up by rubbing."

float

Meaning: to stay on the surface of a liquid without sinking

अर्थ: तैरना

"Empty bottles float on water."

sink

Meaning: to go down below the surface of a liquid

अर्थ: डूबना

"Stones sink in water."

porous

Meaning: full of tiny holes that let air or liquid pass

अर्थ: छिद्रयुक्त/झरझरा

"Pumice is a porous rock that can float."

NCERT Solutions Class 8 Science - Curiosity Chapter 5 – Exploring Forces

Chapter Introduction

Watch Video Lecture

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Important Points

Practice MCQ Questions (67 questions)

Q1. What is a force in science?

Q2. Which action best shows a PUSH being applied?

Q3. Which action best shows a PULL being applied?

Q4. Which unit is used to measure force in SI?

Q5. In Activity 5.1, moving a box in many ways illustrates that:

Q6. A force can:

Q7. If a moving ball is kicked in its direction of motion, its speed usually:

Q8. Turning a bicycle handle mainly shows a force that:

Q9. Squeezing a rubber ball demonstrates that a force can:

Q10. Which statement is TRUE?

Q11. Muscular force is a type of:

Q12. Which example uses muscular force?

Q13. A moving box on a rough floor stops because of:

Q14. Friction acts in a direction that:

Q15. On which surface will a sliding lunchbox likely travel the farthest?

Q16. Air and water offer:

Q17. Streamlined shapes in planes and ships are mainly to:

Q18. Friction between two solids arises chiefly due to:

Q19. If road becomes rougher, a coasting bicycle will stop:

Q20. Which statement about friction is CORRECT?

Q21. Magnetic force can be observed when:

Q22. Ring magnets placed with like poles facing show:

Q23. Electrostatic force is demonstrated when a rubbed plastic scale:

Q24. Two balloons rubbed with wool and then released near each other usually:

Q25. Electrostatic force is a:

Q26. Like charges ______ and unlike charges ______.

Q27. Gravity is a force that is always:

Q28. Objects thrown upward slow down because:

Q29. A stone dropped from a height falls vertically mainly due to:

Q30. Which is a NON-contact force?

Q31. Weight of an object is:

Q32. SI unit of weight is:

Q33. A spring balance directly measures:

Q34. On Earth, 1 small division on a spring balance reads 0.2 N. Five small divisions indicate:

Q35. If two objects of different masses are hung on the same spring balance one by one, the heavier object shows:

Q36. Mass is measured in:

Q37. Mass of a body on Earth and Moon is:

Q38. Weight of the same object on the Moon compared to Earth is:

Q39. A beam balance compares:

Q40. In everyday language, ‘weight 10 kg’ is commonly used, but scientifically correct phrasing would be:

Q41. A tightly closed empty plastic bottle pushed into water feels an upward push due to:

Q42. If buoyant force equals the gravitational force on an immersed object, the object:

Q43. If weight is greater than upthrust, an object in liquid will:

Q44. Buoyant force depends, among other factors, on the liquid’s:

Q45. Archimedes’ principle states that the upthrust equals the:

Q46. Pumice can float on water mainly because it is:

Q47. A mug feels lighter when submerged in water due to:

Q48. Ships float although made of steel because their average density:

Q49. If salt is added to water making it denser, a floating object will generally:

Q50. Two equal-sized blocks, wood and iron, placed in water—wood floats and iron sinks. The correct reason is:

Q51. Pressing the bicycle brake pads on the rim stops the wheel mainly due to:

Q52. Cyclists pedalling harder against wind show that force can:

Q53. On a slope, a bicycle speeds up even without pedalling because:

Q54. The bell on a bicycle makes sound due to:

Q55. Pushing a table and feeling a force on your hand illustrates that:

Q56. Which pair correctly matches force type to example?

Q57. When two surfaces are smoother, the friction between them usually:

Q58. If like poles of two magnets face each other, the magnets:

Q59. When an object is at rest with many forces acting, it may be because the forces are:

Q60. Which instrument is best for directly measuring an object’s WEIGHT in the lab?

Q61. Which is NOT an effect of a force?

Q62. If two students push the same box from opposite sides with equal force, the box:

Q63. A skydiver falling down experiences gravity downward and air friction upward. As speed increases, air friction:

Q64. Which statement about mass and weight is CORRECT?

Q65. When a plastic comb is rubbed on dry hair and then brought near tiny paper bits, they jump to the comb due to:

Q66. Objects thrown upward finally come down because:

Q67. A denser liquid generally exerts ______ buoyant force on the same object compared to a less dense liquid.