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I. Chapter Summary:

This chapter introduces students to the concept of force and Newton’s three laws of motion. It explains how a force can change the state of motion or shape of a body. Students learn about the concepts of inertia, mass, and momentum, and their mathematical relationships. Newton’s laws—First (Law of Inertia), Second (F=ma), and Third (Action–Reaction)—are explained with real-life examples and applications. The chapter lays the foundation for understanding dynamics in Physics.

II. Key Concepts Covered:

Concept	Description
Force	A push or pull that changes or tries to change the state of motion or shape of a body.
Balanced & Unbalanced Forces	Balanced: no change in motion; Unbalanced: causes acceleration.
Inertia	The tendency of an object to resist change in its state of motion.
Newton’s First Law	A body remains in its state of rest or uniform motion unless acted upon by an external unbalanced force.
Mass	Measure of inertia. Greater mass → greater inertia.
Momentum	Product of mass and velocity (p = mv); vector quantity.
Newton’s Second Law	Force is the product of mass and acceleration (F = ma).
Newton’s Third Law	Every action has an equal and opposite reaction.
Law of Conservation of Momentum	Total momentum remains constant in an isolated system (no external force).

III. Important Questions:

(A) Multiple Choice Questions (1 Mark):

1. Which law explains why passengers jerk forward in a moving bus when it stops suddenly?
   a) Newton’s 1st Law ✅
   b) Newton’s 2nd Law
   c) Newton’s 3rd Law
   d) Law of Gravitation
2. Momentum has the unit:
   a) kg/m
   b) kg·m/s ✅
   c) m/s
   d) N·s
3. Which of the following is an example of Newton’s third law?
   a) Rocket launching ✅
   b) Ball rolling on floor
   c) Object falling freely
   d) Tug-of-war balance
4. Which of the following has more inertia?
   a) A 10 kg bag of cotton
   b) A 10 kg iron block ✅
   c) A 1 kg rubber ball
   d) A feather

(B) Short Answer Questions (2/3 Marks):

1. Define momentum. Write its SI unit.
2. State Newton’s second law of motion and give a mathematical formula.
3. Why is it advised to tie luggage with a rope on the roof of a bus?
4. Explain action and reaction forces with an example.
   – PYQ 2021

(C) Long Answer Questions (5 Marks):

1. State and explain all three Newton’s laws of motion with examples.
2. Derive the mathematical formulation of Newton’s second law.
3. Two bodies of masses 2 kg and 4 kg are moving with velocities 3 m/s and 1 m/s respectively. Find total momentum before and after collision (assuming perfectly elastic head-on collision).
4. Explain the law of conservation of momentum with an example. Prove it using the second law of motion.
   – PYQ 2020, 2022

(D) HOTS (Higher Order Thinking Skills):

1. A bullet of mass 10 g is fired from a gun of mass 2 kg. If the bullet moves with a velocity of 400 m/s, calculate the recoil velocity of the gun.
2. A cricket player lowers his hands while catching a ball. Explain in terms of impulse and Newton’s laws.

IV. Key Formulas/Concepts:

Formula	Explanation
Force (F)=matext{Force (F)} = maForce (F)=ma	Force is mass × acceleration
p=mvp = mvp=mv	Momentum = mass × velocity
Change in momentum=mv−mutext{Change in momentum} = mv – muChange in momentum=mv−mu	Final momentum – initial momentum
F=mv−mutF = frac{mv – mu}{t}F=tmv−mu​	Newton’s 2nd law in terms of momentum
Impulse = Force × Time	Product of force and time interval
Conservation of momentum: m1u1+m2u2=m1v1+m2v2m_1u_1 + m_2u_2 = m_1v_1 + m_2v_2m1​u1​+m2​u2​=m1​v1​+m2​v2​	In absence of external force

V. Deleted Portions (CBSE 2025–2026):

 No portions have been deleted from this chapter as per the rationalized NCERT textbooks (2025–26).

VI. Chapter-Wise Marks Bifurcation (Estimated – CBSE 2025–2026):

Chapter	Estimated Marks	Type of Questions Typically Asked
Force and Laws of Motion	8–10 marks	Laws with examples, derivations, numericals, conceptual questions

VII. Previous Year Questions (PYQs):

Year	Marks	Question
2019	5	State Newton’s laws of motion. Give suitable examples.
2020	3	Derive F = ma using momentum concepts.
2021	2	Why do we jerk backward when a bus suddenly starts?
2022	3	A stone of mass 1 kg is thrown with 10 m/s. Calculate momentum.

VIII. Real-World Application Examples to Connect with Topics:

Concept	Application
Newton’s First Law	Seatbelts in cars (resisting sudden stop/start).
Second Law (F = ma)	Sports (force applied to kick or hit a ball).
Third Law	Rocket propulsion, gun recoil.
Conservation of Momentum	Collisions in space, skating, firing guns.
Impulse	Catching a fast cricket ball by moving hands backward.

IX. Student Tips & Strategies for Success:

 Time Management:

• Spend alternate days revising laws and solving numerical problems.
• Create a summary chart for Newton’s laws with examples.

 Exam Preparation:

• Derivation of F = ma is frequently asked.
• Practice problems on momentum and recoil velocity.
• Draw clear diagrams for explanations (action-reaction, rocket, etc.).

 Stress Management:

• Use hands-on activities like toy cars, pushing objects to visualize forces.
• Watch animated simulations of collisions and motion.

X. Career Guidance & Exploration (Class 9–10 Specific):

Stream	Career Options
Engineering	Mechanical, Aerospace, Robotics Engineer
Research	Physicist, Motion Dynamics Expert
Applied Fields	Sports Biomechanics, Defense Engineer

Entry Platforms:

• NTSE
• National Science Olympiad (NSO)
• CBSE Science Exhibition
• DIY Physics Clubs

XI. Important Notes:

•  Newton’s laws form the foundation of all motion-related physics in higher classes.
•  Be thorough with real-life examples for all three laws.
•  In numericals, write proper units and follow steps clearly.
•  Keep diagrams labeled and neat—especially for explanations.