How Forces Affect Motion — Class 9 MCQs with Answers
Class 9 CBSE Science · Chapter 5
115 practice questions · 33 Easy · 42 Medium · 40 Hard · Updated
Jump to the 6 solved questions
Practise the most important Class 9 CBSE Science questions from Chapter 5, "How Forces Affect Motion". You get 11 timed quizzes made from 115 NCERT-based MCQs, with answers and explanations. The questions are split into 33 Easy, 42 Medium and 40 Hard. Warm up on the basics, then move on to the exam-level questions that top scorers in CBSE Board exams and the JEE & NEET foundation years get right.
To score well in "How Forces Affect Motion", focus on clear concepts in physics, chemistry and biology basics. Each MCQ here is timed and uses exam-style marking (+4 correct, −1 wrong, 0 skipped). This helps you stay accurate when time is short, just as real papers need. Every question has a short explanation, so a wrong answer becomes a quick lesson. It is the fastest way to fix gaps before a test.
Use this chapter for focused revision. Start with the Easy set to check your basics on How Forces Affect Motion, then move to Medium and Hard to practise applying them. Your accuracy, streaks and XP save automatically. This chapter also adds to your overall Class 9 Science mastery score. Try the 6 sample questions below: tap an option to see the answer and a worked explanation. Sign in free to start practising.
How Forces Affect Motion — important questions & MCQs with answers (Class 9 Science)
6 solved questions from this chapter's difficulty levels, each with its answer and explanation. Tap an option to check yourself.
0 of 6 answered
- Q1 of 6Easy
Newton's first law of motion is also called the law of:
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Answer: Inertia
Explanation: Newton's first law says a body stays at rest or in uniform motion unless an external force acts on it — this resistance to a change in motion is called inertia, not acceleration or conservation.
- Q2 of 6Easy
Momentum p of a body is defined as:
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Answer: mv
Explanation: Momentum is defined as p = mv (mass × velocity), not m + v or m/v — those don't even carry momentum's correct unit of kg·m/s.
- Q3 of 6Medium
F = ma is the mathematical form of:
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Answer: Second law
Explanation: F = ma is the mathematical form of Newton's second law: net force equals mass times acceleration.
- Q4 of 6Medium
Assertion (A): On a perfectly frictionless floor, a moving object keeps moving with constant velocity without any force being applied. Reason (R): On a frictionless floor, a net force is still needed to set an object at rest into motion.
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Answer: Both A and R are true but R is not the correct explanation of A
Explanation: Both statements are true. A follows from Newton's first law, since no net force acts to change the velocity; R is about starting motion from rest, so it does not explain A.
- Q5 of 6Hard
A 2 kg ball accelerates from 0 to 10 m/s in 5 s. Force applied =
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Answer: 4 N
Explanation: Acceleration a = Δv/Δt = (10 − 0) m/s ÷ 5 s = 2 m/s². By F = ma, the applied force = 2 kg × 2 m/s² = 4 N.
- Q6 of 6Hard
Assertion (A): A 50 kg box at rest on a frictionless floor is pushed with a constant net force of 20 N, so it moves 1.8 m in 3 s. Reason (R): By Newton's second law, the acceleration of the box is F ÷ m = 0.4 m s⁻².
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Answer: Both A and R are true and R is the correct explanation of A
Explanation: Both statements are true. With a = 0.4 m s⁻² and u = 0, s = ½ × 0.4 × 3² = 1.8 m, so R leads to A.
How Forces Affect Motion notes: key concepts (Class 9 Science)
Force changes an object's state of motion, and Newton's three laws state exactly how. This chapter covers inertia, the relationship between force and momentum, action-reaction pairs, and the conservation of momentum in collisions.
- Force
- A push or pull that can change an object's speed, direction or shape; it is a vector quantity.
- Balanced and unbalanced forces
- Balanced forces cancel and leave motion unchanged; only an unbalanced force can start, stop, speed up, slow down or turn an object.
- Newton's first law
- An object stays at rest or in uniform straight-line motion unless acted upon by an unbalanced external force.
- Inertia
- The natural tendency of an object to resist a change in its state of motion; the first law is therefore also called the law of inertia.
- Mass as a measure of inertia
- The greater an object's mass the greater its inertia, which is why a heavier object is harder to start or stop.
- Types of inertia
- Inertia of rest, of motion and of direction, illustrated by a passenger lurching backwards, forwards and sideways in a bus.
- Momentum
- The product of mass and velocity, a vector measuring the 'quantity of motion' and measured in kg·m/s.
- Newton's second law
- The rate of change of momentum is proportional to the applied force and occurs in the direction of that force, giving F = ma.
- Why follow-through reduces force
- Increasing the time over which momentum changes reduces the force, which is why a cricketer pulls their hands back while catching.
- Newton's third law
- For every action there is an equal and opposite reaction; the two act on DIFFERENT bodies and so never cancel.
- Action-reaction pairs
- The recoil of a gun, the walking of a person pushing back on the ground, and the launch of a rocket are all third-law pairs.
- Conservation of momentum
- In the absence of an external force, the total momentum of a system before an interaction equals the total after it.
- Applying conservation in collisions
- Equating total momentum before and after allows an unknown velocity to be found without knowing the forces involved.
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How Forces Affect Motion — FAQs
What are the key concepts in Class 9 Science How Forces Affect Motion?+
Force changes an object's state of motion, and Newton's three laws state exactly how. This chapter covers inertia, the relationship between force and momentum, action-reaction pairs, and the conservation of momentum in collisions. Key ideas include Force, Balanced and unbalanced forces, Newton's first law, Inertia, Mass as a measure of inertia, Types of inertia.
What does Class 9 Science Chapter 5 (How Forces Affect Motion) cover on XamBaaz?+
It has 115 NCERT-based MCQs on "How Forces Affect Motion": 33 Easy, 42 Medium and 40 Hard. Together they make 11 timed quizzes, and you never get the same set twice. Every question has an instant explanation. They help you prepare for CBSE Board exams and the JEE & NEET foundation years.
Are these "How Forces Affect Motion" questions free to practise?+
Yes. Sign in with Google to practise "How Forces Affect Motion" free. Full unlimited access is ₹999/year. One year from the day you pay. You stay in Class 9 till 31 March; on 1 April your account moves up to Class 10 and the rest of your year carries over. No chapter is charged separately.
How should I revise "How Forces Affect Motion" for the exam?+
Start with the Easy quiz to check your basics, then try Medium and Hard to practise applying them. There are 11 timed quizzes on this chapter, so you can come back for a fresh set instead of one you have seen. Read each explanation, retry the questions you miss, and track your accuracy until it stays high.
Are these "How Forces Affect Motion" MCQs available with answers?+
Yes. 6 sample questions are on this page with answers: tap an option, or "Show answer", to see the correct option and a step-by-step explanation. Sign in free with Google to start practising, with instant scoring.
Is there negative marking in the "How Forces Affect Motion" quizzes?+
Yes. The timed quizzes use exam-style marking: +4 for a right answer, −1 for a wrong one and 0 for a skip. MHT-CET and CBSE board papers have no negative marking. Our mocks for those are scored their way.
What are the important questions from How Forces Affect Motion (Class 9 Science)?+
The questions that matter most test Force, Balanced and unbalanced forces, Newton's first law, Inertia, Mass as a measure of inertia, Types of inertia. This page shows 6 solved important MCQs with answers and explanations. Sign in to practise all 115 questions on the chapter as timed quizzes.
Is there an online quiz for How Forces Affect Motion?+
Yes — Class 9 Science How Forces Affect Motion has timed online quizzes at Easy, Medium and Hard levels, with instant scoring and a worked explanation on every question. The first quiz on the chapter is free.
Are there question answers and extra questions for How Forces Affect Motion (Class 9 Science)?+
Yes. This page has 6 solved questions on How Forces Affect Motion, each with the correct answer and a short explanation. Sign in to practise all 115 questions on the chapter as timed quizzes.
Are there assertion–reason and case study questions for How Forces Affect Motion (Class 9 Science)?+
Yes. The How Forces Affect Motion question bank has 9 assertion–reason questions and 12 case-based (case study) questions in the CBSE board format, alongside the regular MCQs. Each comes with the answer and a worked explanation. Sign in to practise them in timed quizzes.