What is Forces Exercises in Class 8 Science NCERT?

The Class 8 Science NCERT Chapter 5 — Exploring Forces exercise section tests students on all the key concepts covered in the chapter, including NCERT exercises, force questions, friction questions, competency-based questions. It includes multiple-choice questions (MCQs), assertion-reason questions…

What does the NCERT Class 8 Science Exploring Forces exercise section cover?

The Class 8 Science NCERT Chapter 5 u2014 Exploring Forces exercise section tests students on all the key concepts covered in the chapter, including NCERT exercises, force questions, friction questions, competency-based questions. It includes multiple-choice questions (MCQs), assertion-reason questions, short-answer questions, long-answer questions, and competency-based questions that align with the NCERT Curiosity textbook. Working through these exercises helps Class 8 students reinforce their conceptual understanding, prepare for classroom assessments, and build exam readiness for CBSE school tests. Each question links back to a specific section of the chapter so students can revise the theory alongside the practice.

How should Class 8 students approach the Exploring Forces exercises?

Class 8 students should approach the Exploring Forces exercises by first revising the main theory and definitions from each part of the chapter, especially around NCERT exercises and force questions. Start with the MCQs and assertion-reason questions to quickly test recall, then attempt the short-answer questions that need a one or two-line explanation, and finally tackle the long-answer and competency-based questions that require applying concepts to new situations. Write neat diagrams wherever the question involves a process, cycle, or setup, and always use NCERT-style vocabulary in your answers to match CBSE marking schemes.

Are these Exploring Forces questions competency-based as per NEP 2020?

Yes, the Exploring Forces exercise set follows the NEP 2020 competency-based education (CBE) framework used by CBSE and NCERT for Class 8 Science. Instead of only asking students to recall definitions, many questions are scenario-based and require applying the concept to real-life situations, analysing data, or evaluating claims. This matches Bloom's Taxonomy levels L3 (Apply), L4 (Analyse), and L5 (Evaluate), going beyond rote learning. Students practising these questions build the higher-order thinking skills that modern CBSE school exams increasingly assess, and also prepare well for competitive foundation tests in later years.

Which NCERT Curiosity sections are tested in Chapter 5 exercises?

The Chapter 5 u2014 Exploring Forces exercise set systematically tests every major section of the NCERT Curiosity Class 8 Science textbook for this chapter. Topics covered include NCERT exercises, force questions, friction questions, competency-based questions. Every in-text question, activity-linked question, and end-of-chapter question from the Curiosity book is represented, so students can be confident that completing this exercise set gives them full coverage of the NCERT syllabus. Teachers also frequently pick questions from these sections for school unit tests and half-yearly exams, making thorough practice essential for strong performance.

How do assertion-reason questions work in this Class 8 Science chapter?

Assertion-reason questions in the Class 8 Science Exploring Forces exercise set present two statements u2014 an Assertion (A) and a Reason (R) u2014 and ask students to judge whether each is true and whether R correctly explains A. Students pick from four standard options: both true with R explaining A, both true but R not explaining A, A true and R false, or A false. This format tests whether Class 8 learners genuinely understand the cause-and-effect relationships behind NCERT exercises, not just surface facts. Mastering this format is valuable because CBSE Class 10 board exams use the same pattern.

What is the best revision strategy before attempting these exercises?

The best revision strategy before attempting Exploring Forces exercises is to read through all theory parts of NCERT Curiosity Chapter 5 once, write down the key terms such as NCERT exercises, force questions, friction questions, competency-based questions in your own words, and then re-do all activities mentally to understand the underlying concept. Next, make a one-page mind map linking the main ideas. Only then attempt the exercise questions u2014 first without looking back, then self-correcting. This active-recall approach builds much stronger long-term memory than repeatedly re-reading the textbook, and is widely recommended by CBSE teachers for Class 8 Science preparation.

What does the NCERT Class 8 Science Exploring Forces exercise section cover?

The Class 8 Science NCERT Chapter 5 — Exploring Forces exercise section tests students on all the key concepts covered in the chapter, including NCERT exercises, force questions, friction questions, competency-based questions. It includes multiple-choice questions (MCQs), assertion-reason questions, short-answer questions, long-answer questions, and competency-based questions that align with the NCERT Curiosity textbook. Working through these exercises helps Class 8 students reinforce their conceptual understanding, prepare for classroom assessments, and build exam readiness for CBSE school tests. Each question links back to a specific section of the chapter so students can revise the theory alongside the practice.

How should Class 8 students approach the Exploring Forces exercises?

Class 8 students should approach the Exploring Forces exercises by first revising the main theory and definitions from each part of the chapter, especially around NCERT exercises and force questions. Start with the MCQs and assertion-reason questions to quickly test recall, then attempt the short-answer questions that need a one or two-line explanation, and finally tackle the long-answer and competency-based questions that require applying concepts to new situations. Write neat diagrams wherever the question involves a process, cycle, or setup, and always use NCERT-style vocabulary in your answers to match CBSE marking schemes.

Are these Exploring Forces questions competency-based as per NEP 2020?

Yes, the Exploring Forces exercise set follows the NEP 2020 competency-based education (CBE) framework used by CBSE and NCERT for Class 8 Science. Instead of only asking students to recall definitions, many questions are scenario-based and require applying the concept to real-life situations, analysing data, or evaluating claims. This matches Bloom's Taxonomy levels L3 (Apply), L4 (Analyse), and L5 (Evaluate), going beyond rote learning. Students practising these questions build the higher-order thinking skills that modern CBSE school exams increasingly assess, and also prepare well for competitive foundation tests in later years.

Which NCERT Curiosity sections are tested in Chapter 5 exercises?

The Chapter 5 — Exploring Forces exercise set systematically tests every major section of the NCERT Curiosity Class 8 Science textbook for this chapter. Topics covered include NCERT exercises, force questions, friction questions, competency-based questions. Every in-text question, activity-linked question, and end-of-chapter question from the Curiosity book is represented, so students can be confident that completing this exercise set gives them full coverage of the NCERT syllabus. Teachers also frequently pick questions from these sections for school unit tests and half-yearly exams, making thorough practice essential for strong performance.

How do assertion-reason questions work in this Class 8 Science chapter?

Assertion-reason questions in the Class 8 Science Exploring Forces exercise set present two statements — an Assertion (A) and a Reason (R) — and ask students to judge whether each is true and whether R correctly explains A. Students pick from four standard options: both true with R explaining A, both true but R not explaining A, A true and R false, or A false. This format tests whether Class 8 learners genuinely understand the cause-and-effect relationships behind NCERT exercises, not just surface facts. Mastering this format is valuable because CBSE Class 10 board exams use the same pattern.

What is the best revision strategy before attempting these exercises?

The best revision strategy before attempting Exploring Forces exercises is to read through all theory parts of NCERT Curiosity Chapter 5 once, write down the key terms such as NCERT exercises, force questions, friction questions, competency-based questions in your own words, and then re-do all activities mentally to understand the underlying concept. Next, make a one-page mind map linking the main ideas. Only then attempt the exercise questions — first without looking back, then self-correcting. This active-recall approach builds much stronger long-term memory than repeatedly re-reading the textbook, and is widely recommended by CBSE teachers for Class 8 Science preparation.

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Exploring Forces — Exercises

🎓 Class 8 Science CBSE Theory Ch 5 — Coal and Petroleum ⏱ ~20 min

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Chapter Summary at a Glance

Chapter 5 opened with simple questions — why is pedaling uphill harder, why things fall, why knives are sharp — and revealed that one idea, force, is behind all of them. Here is a quick bird's-eye view of the types of force we met.

Category	Force	Needs Contact?	Key Example
Contact	Muscular force	Yes	Pushing a door, lifting books
Contact	Friction	Yes	Ball slowing on the floor
Non-Contact	Magnetic force	No	Magnet attracting iron pins
	Electrostatic force	No	Rubbed balloon attracting hair
	Gravitational force	No	Apple falling from a tree

Key formulas: Pressure \( P = \dfrac{F}{A} \) (SI unit: pascal, Pa). Weight \( W = m \times g \). Upthrust = weight of fluid displaced (Archimedes' principle).

Key Terms to Remember

Force A push or pull on an object.

Newton (N) SI unit of force.

Net force Resultant of all forces acting.

Balanced Equal and opposite forces — no motion change.

Unbalanced Unequal forces — motion changes.

Muscular Force from contracting muscles.

Friction Contact force opposing relative motion.

Static friction Acts on an object at rest.

Sliding friction Between sliding surfaces.

Rolling friction Between a rolling body and the surface.

Fluid friction (Drag) Resistance from liquids/gases.

Streamlined Shape that cuts through fluid easily.

Magnetic force Between magnets / magnetic materials.

Electrostatic Force between charged objects.

Gravitational Attraction between any two masses.

Weight Force of gravity on an object.

Mass Amount of matter — stays same everywhere.

Pressure Force per unit area, P = F/A.

Pascal (Pa) SI unit of pressure, 1 N/m².

Atmospheric pressure Pressure due to the air above us.

Buoyancy / Upthrust Upward push of a fluid.

Archimedes' principle Upthrust = weight of fluid displaced.

NCERT Exercises

Attempt each question on your own first — then click the button to compare with the model answer.

1What is force? What is its SI unit?

Force: A force is a push or a pull exerted on an object by another object. It can start or stop motion, change the speed or direction of a moving object, and change the shape of an object. SI Unit: newton (symbol: N).

2State the four effects of force. Give one example of each.

(i) Change in state of motion: A football at rest starts moving when kicked.
(ii) Change in speed: Applying brakes on a bicycle slows it down.
(iii) Change in direction: A batsman hits a ball flying toward him and it goes sideways.
(iv) Change in shape: Pressing soft dough flattens it into a chapati.

3Match each type of force in Column A with the situation in Column B.

Column A	Column B
(i) Muscular force	(a) cricket ball stopping on its own just before touching the boundary line
(ii) Magnetic force	(b) child lifting a school bag
(iii) Frictional force	(c) fruit falling from a tree
(iv) Gravitational force	(d) balloon rubbed on woollen cloth attracting hair strands
(v) Electrostatic force	(e) compass needle pointing North

(i) → (b) Lifting a bag uses the muscles of arms/shoulders.
(ii) → (e) A compass needle aligns with Earth's magnetic field.
(iii) → (a) Friction between ball and ground slows the ball to a stop.
(iv) → (c) Earth's gravity pulls the fruit straight down.
(v) → (d) The rubbed balloon is charged and attracts hair by electrostatic force.

4Name the three types of friction. Give one everyday example of each.

(i) Static friction — when an object is at rest. Example: a heavy trunk that won't budge when you first push it.
(ii) Sliding friction — between surfaces in relative sliding motion. Example: a book you drag across a table.
(iii) Rolling friction — when one surface rolls on another. Example: a bicycle wheel turning on the road.

5Why is rolling friction less than sliding friction?

When a body rolls, only a small portion of its surface touches the ground at any moment, and that contact keeps shifting. The microscopic bumps of the two surfaces don't get enough time to interlock. In sliding, a larger area stays in continuous contact and the bumps catch on each other continuously. Hence rolling friction is much less than sliding friction — this is why wheels and ball bearings are used in almost all machines.

6Give three situations where friction is helpful and three where it is harmful.

Helpful: (i) Walking without slipping. (ii) Brakes stopping a moving vehicle. (iii) Striking a matchstick on a rough strip.

Harmful: (i) Wearing out of shoe soles, tyres and machine parts. (ii) Wastage of fuel energy as heat in engines. (iii) Heating of moving parts, which can damage machinery.

7Why are cyclists (in races) and race cars designed with streamlined shapes?

Air is a fluid and offers resistance (fluid friction or drag) to fast-moving objects. A streamlined body — pointed in front, tapering to the back — allows air to flow smoothly around it, reducing drag. Less drag means the cyclist or race car needs less energy to maintain high speed. That is why racing helmets, suits and car bodies are carefully shaped.

8Define pressure. Why is a knife edge kept sharp? Why does a camel have wide feet?

Pressure is the force acting per unit area. \( P = F/A \); unit: pascal (Pa).

Sharp knife: A sharp edge has a very small contact area. For the same downward force, a small area gives very high pressure, so the knife cuts easily into vegetables or fruit.

Wide camel feet: Camels live on sand. Their wide, padded feet spread the camel's weight over a large area. A larger area reduces the pressure on the sand, so the feet do not sink deep and the animal can walk comfortably.

9Explain buoyancy. Why does a coin sink in water but a ship float?

Buoyancy is the upward force exerted by a fluid on any object immersed in it, arising because fluid pressure increases with depth. By Archimedes' principle, upthrust equals the weight of fluid displaced.

Coin: A solid metal coin has a very small volume, so it displaces a tiny amount of water. That water's weight is much less than the coin's weight, so upthrust cannot balance the weight — the coin sinks.

Ship: Though made of heavy steel, a ship is hollow and has a large volume. It pushes aside a huge quantity of water. The weight of that displaced water is equal to (or greater than) the ship's weight, so the upthrust supports it and the ship floats.

10Your friend is pushing a box on the floor, but the box is not moving. What forces are acting on the box? Are they balanced or unbalanced?

Two main horizontal forces act on the box: (1) the applied push of your friend in one direction, and (2) static friction from the floor in the opposite direction. Since the box does not move, these two forces are equal in magnitude and opposite in direction — they are balanced. The net force is zero, so there is no change in the box's state of motion. (Additionally, the downward weight of the box is balanced by the upward normal reaction from the floor.)

11On the Moon, an object falls more slowly than on Earth. Why?

The Moon has less mass than the Earth, so its gravitational pull on objects is much smaller. The acceleration due to gravity on the Moon is only about 1.6 m/s², compared with 9.8 m/s² on Earth — roughly one-sixth. A smaller gravitational pull means the object gains speed more slowly as it falls. Hence objects on the Moon appear to fall in slow motion.

12What is electrostatic force? Give two examples from daily life.

Electrostatic force is the force exerted by a charged object on another charged or uncharged object without any physical contact. Like charges repel, unlike charges attract.

Example 1: When a plastic comb is rubbed on dry hair and brought near small pieces of paper, the paper pieces jump up and stick to the comb — the charged comb attracts them.
Example 2: On a cold dry day, taking off a woollen sweater makes a crackling sound and sparks can sometimes be seen — charges built up by friction discharge through the air.

Tip for exams: When in doubt, always write: (a) the definition in one line, (b) the formula if any, and (c) a daily-life example. This three-part answer earns full marks in CBSE science papers.

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