Q1. State Newton’s First Law of Motion.
A. A body continues to be in its state of rest or of uniform motion in a straight line unless an external unbalanced force acts on it.
Q2. What is inertia?
A. The tendency of an object to resist a change in its state of motion or rest is called inertia.
Q3. State Newton’s Second Law of Motion.
A. The rate of change of momentum of a body is directly proportional to the unbalanced force applied on it and takes place in the direction of the force.
Formula: F = m × a
Q4. State Newton’s Third Law of Motion.
A. For every action, there is an equal and opposite reaction.
Q5. Define momentum and write its formula.
A. Momentum of a body is the product of its mass and velocity.
Formula: p = m × v
Q6. What is impulse?
A. The product of force and the time duration for which it acts is called impulse.
Formula: Impulse = F × Δt
Q7. Give an example of Newton’s Third Law in daily life.
A. When a person jumps from a boat to the shore, the boat moves backwards.
Q8. Write the SI unit of force and momentum.
A. Force – Newton (N), Momentum – kg·m/s
Q9. Why is it easier to stop a moving cricket ball than a moving truck?
A. Because the momentum of the truck is much greater than that of the ball, so more force is needed to stop it.
Q10. Give two applications of Newton’s First Law.
A.
Q11. Why does a passenger fall backward when a bus starts suddenly?
A. Due to inertia of rest, the passenger's body tends to remain at rest while the bus moves forward suddenly.
Q12. Why does a person fall forward when a moving bus stops suddenly?
A. Due to inertia of motion, the passenger's body tends to keep moving forward when the bus stops suddenly.
Q13. What is the mathematical form of Newton’s Second Law?
A. F = (m × v - m × u) / t or F = m × a
Q14. Name the factors on which momentum depends.
A. Momentum depends on the mass of the body and its velocity.
Q15. Why are seat belts provided in vehicles?
A. To prevent passengers from being thrown forward suddenly in case of an accident by reducing the effect of inertia.
Q16. Why does a gun recoil backward when fired?
A. Due to Newton’s Third Law – the bullet is pushed forward (action), and the gun is pushed backward (reaction).
Q17. State the law of conservation of momentum.
A. The total momentum of an isolated system remains constant if no external force acts on it.
Q18. Give an example of conservation of momentum.
A. When two ice skaters push each other, they move in opposite directions with equal and opposite momentum.
Q19. How does a rocket work based on Newton’s laws?
A. A rocket expels gases at high speed in the downward direction (action), and as a reaction, it moves upward.
Q20. Why does an athlete run before taking a long jump?
A. To gain momentum, which helps him to jump farther due to greater initial velocity.
Q21. Why do objects fall towards the Earth?
A. Due to the gravitational force of attraction between the Earth and the object.
Q22. Why is it difficult to push a stationary heavy box at first?
A. Because of static friction and the inertia of rest which resists motion.
Q23. How is acceleration related to force for a constant mass?
A. For a constant mass, acceleration is directly proportional to the applied unbalanced force (a ∝ F).
Q24. How is acceleration related to mass for a constant force?
A. For a constant force, acceleration is inversely proportional to the mass of the body (a ∝ 1/m).
Q25. Why does a car stop after the engine is switched off even on a straight road?
A. Due to unbalanced forces like friction and air resistance acting on the car.
Q26. State the relationship between momentum and kinetic energy.
A. Kinetic Energy (KE) = p² / (2m), where p is momentum and m is mass.
Q27. Why is it easier to pull a roller than to push it?
A. Pulling reduces the effective normal force and friction, while pushing increases it.
Q28. What is the unit of impulse?
A. The SI unit of impulse is Newton-second (N·s), same as momentum.
Q29. Why do athletes wear spikes while running?
A. To increase friction between their shoes and the ground, preventing slipping.
Q30. Why does a glass tumbler break when it falls on a hard floor but not when it falls on a carpet?
A. On a carpet, the stopping time increases, reducing the force of impact due to impulse effect.