TNPSC Physics Laws of Motion Quiz 2 – Important MCQs with Answers

Concept Booster – TNPSC Laws of Motion Quiz 2

Newton’s laws of motion form the foundation of classical mechanics and are one of the most important topics in TNPSC physics MCQs. These laws explain how objects behave when forces act on them, helping us understand real-life situations like moving vehicles, walking, jumping, and even rocket motion. Most TNPSC laws of motion questions are directly based on concepts like inertia, force, acceleration, and action-reaction pairs.

First Law (Law of Inertia):

The First Law states that an object remains at rest or in uniform motion unless acted upon by an external force. This explains why passengers fall backward when a bus starts suddenly and why dust comes off when a rug is shaken. The resistance of an object to change its state is called inertia, and it depends on mass.

Remember:

• A body resists change in its state (rest or motion)
• Inertia depends on mass
• Example: Passengers fall backward when bus starts

Second Law :

The Second Law of Motion explains the relationship between force, mass, and acceleration. It states that force is equal to the rate of change of momentum, commonly written as:

• $F = ma$F=ma

This means acceleration increases with force and decreases with mass. So, lighter objects accelerate faster, while heavier objects require more force to move.

Remember:

• Force is the rate of change of momentum
• F = ma (force = mass × acceleration)
• Acceleration ∝ force and ∝ 1/mass

Third Law :

The Third Law of Motion states that for every action, there is an equal and opposite reaction. This principle explains everyday actions like walking (we push the ground backward, and it pushes us forward) and rocket propulsion.

Understanding these laws also helps in solving questions related to momentum, friction, and motion. For example, a rolling ball stops due to friction, and a ball thrown upward slows down due to gravity acting opposite to motion.

Remember

• Every action has an equal and opposite reaction
• Action and reaction act on different bodies
• Example: Walking, rocket motion

Important Points to Remember

• Inertia depends on mass (more mass → more inertia)
• Force = mass × acceleration (F = ma)
• Acceleration is directly proportional to force
• Acceleration is inversely proportional to mass
• Momentum = mass × velocity
• Rate of change of momentum = force
• Action and reaction always act on different bodies
• Friction always opposes motion
• Gravity slows down upward motion and speeds up downward motion
• If no external force acts → object continues in same state (rest/motion)

Real-Life Examples of Newton’s Laws

For First Law (Inertia)

• Passengers fall backward when a bus starts suddenly
• Dust comes off when a carpet is shaken
• Seat belts prevent forward motion during sudden stops

Second Law (F = ma)

• An empty cart moves faster than a loaded cart
• Kicking a football is easier than kicking a stone
• Heavier objects require more force to move

Third Law (Action–Reaction)

• Rockets move upward by pushing gases downward
• While walking, we push the ground backward
• Swimming: pushing water backward moves us forward

Most TNPSC questions are based on identifying these real-life applications of Newton’s laws.

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Refer NCERT Physics Class 11 – Laws of Motion chapter for detailed concepts, formulas, and real-life applications.