Science Exploration Notes Class 9 English Medium 2026-27

Science Exploration Chapter 6. How Forces Affect Motion

CBSE Notes New Syllabus: Class 9

Assignments - What Have You Learned?

Chapter 6. How Forces Affect Motion

This assignment is based on the complete chapter and follows the latest CBSE competency-based assessment pattern. It includes objective, descriptive, application-based, case-study and HOTS questions to strengthen conceptual understanding of force, friction, Newton's laws of motion and momentum.

Chapter Assignment

1. One Word Answer

1. A push or pull acting on an object.
2. The SI unit of force.
3. The instrument used to measure force.
4. The combined effect of all forces acting on an object.
5. Equal and opposite forces with zero resultant.
6. The property by which an object resists a change in its state of motion.
7. The force that opposes motion between two surfaces.
8. The product of mass and velocity.
9. The gravitational force acting on an object.
10. The law stated as "For every action, there is an equal and opposite reaction."

2. Fill in the Blanks

1. Force is a __________ quantity because it has magnitude and direction.
2. The SI unit of force is __________.
3. Balanced forces have __________ net force.
4. Unbalanced forces produce __________.
5. Force is measured using a __________.
6. The formula for force is __________.
7. The formula for momentum is __________.
8. Weight is calculated using the formula __________.
9. Friction always acts __________ the direction of motion.
10. Action and reaction act on __________ objects.

3. True or False

1. Force can change the shape of an object.
2. Balanced forces always change the motion of an object.
3. Momentum depends on both mass and velocity.
4. Mass and weight are the same physical quantities.
5. Friction is always harmful.
6. Newton's First Law is also called the Law of Inertia.
7. Action and reaction act on the same object.
8. A body at rest has zero momentum.
9. Weight changes with gravity.
10. Rolling friction is generally less than sliding friction.

4. Match the Following

5. Very Short Answer Questions

1. Define force.
2. Why is force called a vector quantity?
3. State the SI unit of force.
4. What is a balanced force?
5. What is an unbalanced force?
6. Define inertia.
7. Write Newton's First Law of Motion.
8. State Newton's Second Law of Motion.
9. Define momentum.
10. State Newton's Third Law of Motion.

6. Short Answer Questions

1. Explain the characteristics of force.
2. Differentiate between balanced and unbalanced forces.
3. Describe the different effects of force with examples.
4. Explain the concept of inertia with suitable examples.
5. Differentiate between mass and weight.
6. Describe the advantages and disadvantages of friction.
7. Explain different methods of reducing friction.
8. State and explain Newton's Second Law with the formula F = ma.
9. Explain momentum and the factors affecting it.
10. Explain Newton's Third Law with two everyday examples.

7. Long Answer Questions

1. Explain Newton's First, Second and Third Laws of Motion with suitable examples.
2. Describe the concept of force and its effects on the motion of an object.
3. Explain balanced and unbalanced forces with real-life applications.
4. Discuss friction, its advantages, disadvantages and methods of reducing it.
5. Explain momentum, its formula, SI unit and practical applications.
6. Differentiate between mass, weight and momentum.
7. Discuss the applications of Newton's laws in everyday life.
8. Explain why force is considered a vector quantity.
9. Describe how force and momentum are related.
10. Explain the importance of friction in transportation and sports.

8. Case Study Questions

Case Study – 1

A football lying on the ground is kicked by a player and starts moving towards the goal.

1. Which force starts the motion of the football?
2. Are the forces balanced or unbalanced?
3. Which law explains the change in motion?
4. What happens to the momentum of the ball after it is kicked?

Case Study – 2

A passenger standing inside a bus moves backward when the bus starts suddenly.

1. Name the property responsible for this effect.
2. Which law of motion explains this situation?
3. What type of inertia is observed?
4. How can this effect be reduced?

Case Study – 3

A cricket player pulls his hands backward while catching a fast-moving ball.

1. Which law of motion explains this action?
2. Why does the player move the hands backward?
3. How does this reduce the force of impact?
4. How is momentum involved in this situation?

Case Study – 4

A loaded truck and a motorcycle are moving with the same speed on a highway.

1. Which vehicle has greater momentum?
2. Why?
3. Which vehicle requires more force to stop?
4. State the formula for momentum.

Case Study – 5

A swimmer pushes water backward with his hands and moves forward.

1. Which law of motion explains this?
2. Identify the action force.
3. Identify the reaction force.
4. Give one more example based on the same law.

9. Competency-Based Questions

1. Why is force required to change the motion of an object?
2. How can balanced forces keep an object moving with constant velocity?
3. Why do heavy vehicles require a greater braking distance?
4. How does friction help us walk safely?
5. Why are tyre treads made rough?
6. How does lubrication improve the efficiency of machines?
7. Why does a loaded truck have greater momentum than a motorcycle moving at the same speed?
8. Explain why airbags reduce injuries during accidents.
9. Why do action and reaction never cancel each other?
10. How are Newton's laws useful in sports and transportation?

10. HOTS Questions

1. A bus and a bicycle are moving with the same speed. Which one has greater momentum? Justify your answer.
2. Why does a person slip more easily on a wet floor than on a dry floor?
3. Explain why a rocket can move upward even though there is no air in space.
4. Why does a cricketer move his hands backward while catching a fast ball?
5. Can an object move with zero net force? Explain with an example.
6. Why do action and reaction forces never balance each other?
7. How would life be affected if there were no friction on Earth?
8. A body has a large mass but is at rest. Does it have momentum? Give reasons.
9. Why is force considered a vector quantity while mass is a scalar quantity?
10. How do Newton's laws help engineers design safer vehicles?