TNPSC Physics Laws of Motion Quiz 3

Physics Laws of Motion Quiz –Detailed Explanation For All Questions

This Physics laws of Motion Quiz concept booster will help you clearly understand the important ideas behind each question, including force, inertia, momentum, and Newton’s laws of motion. Instead of just memorizing answers, this section explains the concepts with simple explanations and real-life examples.

By going through this physics laws of motion quiz concept booster, you can strengthen your fundamentals, improve your accuracy, and easily handle similar questions in the TNPSC exam.

Q1. Who introduced the concept of force and motion laws in classical mechanics?

The fundamental laws of motion in classical mechanics were formulated by Isaac Newton. These laws explain how objects move and how forces affect that motion. Newton’s work laid the foundation for physics and is still widely used.

Key Points:
• Laws of motion were introduced by Isaac Newton
• Foundation of classical mechanics
• Explain relationship between force and motion
• Widely used in science and engineering

Real-life Example:
When you push a stationary object like a chair, it starts moving only after applying force.

Answer: Isaac Newton

Q2. What happens when the net force acting on an object is zero?

When the net force acting on an object is zero, there is no acceleration. The object will either remain at rest or continue moving with constant velocity in a straight line. This is explained by Newton’s First Law of Motion.

Key Points:
• Net force = 0 → No acceleration
• Object remains at rest or moves uniformly
• Based on Newton’s First Law
• Forces are balanced

Real-life Example:
A book resting on a table stays still because forces acting on it are balanced.

Answer: It remains at rest or moves uniformly

Q3. Force is a:

Force is a vector quantity because it has both magnitude and direction. To fully describe a force, we must know how strong it is and the direction in which it acts.

Key Points:
• Force has magnitude and direction
• It is a vector quantity
• Direction affects motion
• Represented using arrows

Real-life Example:
Pushing a box in different directions changes its movement depending on the direction of force.

Answer: Vector quantity

Q4. Which factor does NOT affect momentum?

Momentum depends only on mass and velocity of an object. It is calculated as the product of mass and velocity. Temperature does not influence momentum.

Key Points:
• Momentum = mass × velocity
• Depends only on mass and velocity
• Temperature has no effect
• Important in motion analysis

Real-life Example:
A fast-moving truck has more momentum than a bicycle due to its mass and speed, not temperature.

Answer: Temperature

Q5. If force is doubled and mass remains constant, acceleration will:

According to Newton’s Second Law, acceleration is directly proportional to force when mass is constant. So, if the force is doubled, the acceleration will also double.

Key Points:
• Acceleration ∝ Force
• Mass remains constant
• Doubling force doubles acceleration
• Based on Second Law

Real-life Example:
If you push a trolley harder, it moves faster because acceleration increases.

Answer: Double

Q6. A person standing in a moving bus suddenly falls sideways when the bus turns. This is due to:

When a bus suddenly changes direction, the body of the person tends to continue in its original direction due to inertia. This resistance to change in direction is called inertia of direction.

Key Points:
• Inertia resists change in motion
• Applies to direction change
• Part of Newton’s First Law
• Seen in moving vehicles

Real-life Example:
Passengers lean sideways when a bus takes a sharp turn.

Answer: Inertia of direction

Q7. The unit Newton (N) is equal to:

The SI unit of force is Newton. It is defined as the force required to accelerate a mass of 1 kg by 1 m/s². Hence, 1 Newton = 1 kg·m/s².

Key Points:
• SI unit of force is Newton
• Derived unit
• Based on mass, length, and time
• Formula: F = ma

Real-life Example:
Used in physics problems involving force and motion.

Answer: kg·m/s²

Q8. Which law is used in designing seat belts?

Seat belts are designed based on Newton’s First Law of Motion. When a vehicle stops suddenly, the body tends to continue moving forward due to inertia. Seat belts provide the necessary force to stop the body safely.

Key Points:
• Based on First Law (Inertia)
• Prevents forward motion during sudden stop
• Improves safety
• Common in vehicles

Real-life Example:
Seat belts prevent passengers from being thrown forward during accidents.

Answer: First Law

Q9. A fast-moving truck has more momentum than a slow bicycle because:

Momentum depends on both mass and velocity. A truck has a larger mass and usually higher speed compared to a bicycle, resulting in greater momentum.

Key Points:
• Momentum = mass × velocity
• Depends on both factors
• Higher mass → higher momentum
• Higher speed → higher momentum

Real-life Example:
Stopping a truck is harder than stopping a bicycle.

Answer: It has greater mass and velocity

Q10. The change in momentum is called:

The change in momentum of an object is known as impulse. It is produced when a force acts on an object over a period of time.

Key Points:
• Impulse = change in momentum
• Depends on force and time
• Important in collisions
• Unit: N·s

Real-life Example:
Catching a ball by moving hands backward increases time, reducing impact force.

Answer: Impulse

Q11. Impulse depends on:

Impulse depends on both the magnitude of force applied and the duration for which it acts. Greater force or longer time results in greater impulse.

Key Points:
• Impulse = Force × Time
• Depends on two factors
• Important in safety design
• Related to momentum change

Real-life Example:
Airbags increase time of impact, reducing injury.

Answer: Force and time

Q12. Why are roads curved on turns?

Roads are curved or banked to provide the necessary centripetal force required for vehicles to move safely along a curved path without skidding.

Key Points:
• Provides centripetal force
• Helps in safe turning
• Reduces skidding
• Used in highways

Real-life Example:
Vehicles can take turns safely on curved roads without slipping.

Answer: To provide centripetal force

Q13. When a balloon is released, it moves randomly due to:

When air escapes from a balloon, it exerts force in one direction, and the balloon moves in the opposite direction. This is explained by Newton’s Third Law of Motion (action-reaction).

Key Points:
• Based on Third Law
• Action and reaction forces
• Opposite direction movement
• Applies in rockets

Real-life Example:
A released balloon flies unpredictably as air rushes out.

Answer: Action-reaction forces

Q14. Which quantity remains conserved in an isolated system?

In an isolated system where no external forces act, the total momentum remains constant. This is known as the law of conservation of momentum.

Key Points:
• Momentum is conserved
• No external force required
• Applies in collisions
• Important physics principle

Real-life Example:
Recoil of a gun is due to conservation of momentum.

Answer: Momentum

Q15. A force of 10 N acts on a 2 kg object. Acceleration is:

Using Newton’s Second Law (F = ma), acceleration is calculated as force divided by mass. So, 10 ÷ 2 = 5 m/s².

Key Points:
• F = ma
• a = F/m
• Direct calculation
• Unit: m/s²

Real-life Example:
Lighter objects accelerate more easily when pushed.

Answer: 5 m/s²

Q16. Which condition increases stopping distance of a vehicle?

Stopping distance increases with speed because higher speed means greater momentum, requiring more distance to come to rest.

Key Points:
• Higher speed → more momentum
• More distance needed to stop
• Important in road safety
• Affects braking

Real-life Example:
Fast cars take longer to stop compared to slow ones.

Answer: Higher speed

Q17. Why do athletes run before long jump?

Athletes run before jumping to increase their momentum. Greater momentum helps them travel a longer distance in the air.

Key Points:
• Momentum increases with speed
• Helps in longer jump
• Used in sports
• Improves performance

Real-life Example:
Sprinters take a run-up before jumping to cover more distance.

Answer: To gain momentum

Q18. Which law is used in swimming?

Swimming works on Newton’s Third Law. The swimmer pushes water backward, and in reaction, water pushes the swimmer forward.

Key Points:
• Third Law: Action = Reaction
• Opposite forces
• Helps in movement
• Seen in swimming and rowing

Real-life Example:
Pushing water backward helps the swimmer move forward.

Answer: Third Law

Q19. If action force increases, reaction force will:

According to Newton’s Third Law, action and reaction forces are always equal and opposite. So, if action force increases, reaction force also increases equally.

Key Points:
• Action = Reaction
• Equal in magnitude
• Opposite in direction
• Always occur in pairs

Real-life Example:
Pushing a wall harder results in equal force applied back on you.

Answer: Increase equally

Q20. A lighter object accelerates faster than a heavier one under same force because:

Acceleration is inversely proportional to mass. A lighter object has less inertia, so it accelerates more easily under the same force.

Key Points:
• a ∝ 1/m
• Less mass → more acceleration
• Less inertia
• Based on Second Law

Real-life Example:
A small ball moves faster than a heavy stone when pushed with same force.

Answer: Less inertia

Final Revision Tips

• Remember the 3 Laws:
👉 First Law – Inertia (no change without force)
👉 Second Law – F = ma (force causes acceleration)
👉 Third Law – Action = Reaction

• Momentum formula is very important → mass × velocity
👉 More mass or speed = more momentum

• Impulse = Force × Time
👉 Increasing time reduces impact force (important in safety questions)

• Unit-based questions are common
👉 Force = Newton (kg·m/s²)
👉 Acceleration = m/s²

• Inertia types → frequently asked
👉 Inertia of rest, motion, direction

• Real-life application questions are important
👉 Seat belts → First Law
👉 Swimming → Third Law
👉 Turning bus → Inertia of direction

• Numerical questions are easy scoring
👉 Use F = ma carefully (check units)

• Common trap:
👉 Temperature does NOT affect momentum

• Always read question carefully
👉 Words like “NOT”, “ONLY”, “ALWAYS” are important

Most Expected TNPSC Questions from Laws of Motion

• Questions based on Newton’s Laws (direct concept)
• Numerical problems using F = ma
• Momentum comparison questions
• Real-life application (seat belt, walking, swimming)
• Impulse and change in momentum

For more detailed explanation, refer:
🔗 NCERT Class 11 Physics – Laws of Motion