MCQ Physics Chapter–5: Laws of Motion, HS 1st Year

 

1. What is the unit of work and energy in the International System (SI)?

   • A) Newton
   • B) Joule
   • C) Watt
   • D) Erg
     Answer: B) Joule

2. Which of the following is a scalar quantity?

   • A) Displacement
   • B) Velocity
   • C) Kinetic Energy
   • D) Force
     Answer: C) Kinetic Energy

3. The work done by a force on an object is zero when:

   • A) The object moves in the direction of the force.
   • B) The object does not move.
   • C) The object moves perpendicular to the direction of the force.
   • D) Both B and C.
     Answer: D) Both B and C.

4. The work-energy theorem states that:

   • A) The work done by a force on a body is equal to the change in its momentum.
   • B) The work done by a force on a body is equal to the change in its kinetic energy.
   • C) The work done by a force on a body is equal to the change in its potential energy.
   • D) None of the above.
     Answer: B) The work done by a force on a body is equal to the change in its kinetic energy.

5. In physics, the concept of power is defined as:

   • A) Work done per unit time.
   • B) Force applied over a distance.
   • C) Energy stored in an object.
   • D) Rate of change of velocity.
     Answer: A) Work done per unit time.

6. Which law states that the change in kinetic energy of a particle is equal to the work done on it by the net force?

   • A) Newton’s First Law
   • B) Newton’s Second Law
   • C) Work-Energy Theorem
   • D) Conservation of Momentum
     Answer: C) Work-Energy Theorem

7. If a mass $m$ has a velocity $v$, its kinetic energy $K$ is given by:

   • A) $K = mv$
   • B) $K = \frac{1}{2}mv^2$
   • C) $K = mg$
   • D) $K = \frac{1}{2}mv$
     Answer: B) $K = \frac{1}{2}mv^2$

8. What is the potential energy of an object of mass $m$ raised to a height $h$ near the Earth's surface?

   • A) $mg$
   • B) $mgh$
   • C) $\frac{1}{2}mv^2$
   • D) $\frac{1}{2}kx^2$
     Answer: B) $mgh$

9. A conservative force is one where:

   • A) Work done depends on the path taken.
   • B) Work done depends only on the initial and final positions.
   • C) Work done is always positive.
   • D) Work done is always zero.
     Answer: B) Work done depends only on the initial and final positions.

10. The work done by the gravitational force when an object is moved in a circular path is:

• A) Equal to the object’s weight.
• B) Zero.
• C) Equal to the distance traveled by the object.
• D) Always positive.
  Answer: B) Zero.

Variable Forces and Work

13. Work done by a variable force is calculated as:

    • A) $F \cdot d$
    • B) $\int F(x) dx$
    • C) $mgh$
    • D) $\frac{1}{2}kx^2$
      Answer: B) $\int F(x) dx$

14. In a system where the force varies with displacement, the work done is graphically represented as:

    • A) The slope of the force-displacement graph.
    • B) The area under the force-displacement graph.
    • C) The tangent of the force-displacement graph.
    • D) None of the above.
      Answer: B) The area under the force-displacement graph.

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Potential Energy and Conservative Forces

15. Which of the following statements is true for a conservative force?

    • A) Work done depends on the path.
    • B) Work done over a closed loop is non-zero.
    • C) Potential energy can be defined for it.
    • D) It always does negative work.
      Answer: C) Potential energy can be defined for it.

16. A spring with a spring constant $k$ is stretched by a displacement $x$. The potential energy stored in the spring is:

    • A) $kx$
    • B) $\frac{1}{2}kx^2$
    • C) $mgh$
    • D) $\frac{1}{2}mv^2$
      Answer: B) $\frac{1}{2}kx^2$

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Work-Energy Theorem

17. Which of the following equations represents the work-energy theorem?

    • A) $\Delta KE = W$
    • B) $KE + PE = 0$
    • C) $F \cdot v = P$
    • D) $W = F \cdot d$
      Answer: A) $\Delta KE = W$

18. A 10-kg block is pushed with a force of 50 N for 5 m. If the force acts along the displacement, the work done is:

    • A) 10 J
    • B) 50 J
    • C) 250 J
    • D) 500 J
      Answer: C) 250 J
      Solution: $W = F \cdot d = 50 \times 5 = 250 \, \text{J}$.

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Power

19. A 1000 W electric heater is used for 5 hours. What is the energy consumed in kilowatt-hours (kWh)?

    • A) 1 kWh
    • B) 5 kWh
    • C) 5000 kWh
    • D) 100 kWh
      Answer: B) 5 kWh
      Solution: Energy = Power × Time = $1000 \, \text{W} \times 5 \, \text{h} = 5 \, \text{kWh}$.

20. Power is a scalar quantity because:

    • A) It is the dot product of force and velocity.
    • B) It depends on force and direction.
    • C) It has both magnitude and direction.
    • D) None of the above.
      Answer: A) It is the dot product of force and velocity.

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Collisions

21. In a perfectly inelastic collision:

    • A) Kinetic energy is conserved.
    • B) Momentum is conserved but not kinetic energy.
    • C) Both momentum and kinetic energy are conserved.
    • D) Neither momentum nor kinetic energy is conserved.
      Answer: B) Momentum is conserved but not kinetic energy.

22. Two identical objects collide elastically. After the collision:

    • A) They stick together.
    • B) Both come to rest.
    • C) They exchange their velocities.
    • D) One stops, and the other continues with twice the velocity.
      Answer: C) They exchange their velocities.

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Conservation of Mechanical Energy

23. A ball of mass $1 \, \text{kg}$ is dropped from a height of $10 \, \text{m}$. What is its total mechanical energy just before hitting the ground? (Take $g = 10 \, \text{m/s}^2$)

    • A) $10 \, \text{J}$
    • B) $50 \, \text{J}$
    • C) $100 \, \text{J}$
    • D) $200 \, \text{J}$
      Answer: C) $100 \, \text{J}$
      Solution: $E = mgh = 1 \cdot 10 \cdot 10 = 100 \, \text{J}$.

24. The mechanical energy of a system is conserved if:

    • A) Only frictional forces act.
    • B) Only conservative forces act.
    • C) Non-conservative forces are present.
    • D) Both conservative and non-conservative forces act.
      Answer: B) Only conservative forces act.

Energy and Its Types

25. Which of the following is NOT an example of potential energy?

    • A) Water stored in a dam
    • B) A compressed spring
    • C) A moving vehicle
    • D) A stretched rubber band
      Answer: C) A moving vehicle

26. What happens to the total mechanical energy of a system when only conservative forces act?

    • A) It increases.
    • B) It decreases.
    • C) It remains constant.
    • D) It fluctuates.
      Answer: C) It remains constant.

27. A block of mass $m$ slides down a frictionless inclined plane of height $h$. Its velocity at the bottom is given by:

    • A) $\sqrt{2gh}$
    • B) $\sqrt{gh}$
    • C) $2gh$
    • D) $\frac{1}{2}gh$
      Answer: A) $\sqrt{2gh}$
      Solution: Using $v^2 = 2gh$, $v = \sqrt{2gh}$.

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Power Calculations

28. A machine does $200 \, \text{J}$ of work in $10 \, \text{s}$. What is its power output?

    • A) $2 \, \text{W}$
    • B) $20 \, \text{W}$
    • C) $200 \, \text{W}$
    • D) $1000 \, \text{W}$
      Answer: B) $20 \, \text{W}$
      Solution: $P = \frac{W}{t} = \frac{200}{10} = 20 \, \text{W}$.

29. The power of a motor lifting a mass $m$ at constant velocity $v$ is given by:

    • A) $mv$
    • B) $mgh$
    • C) $mvg$
    • D) $F \cdot v$
      Answer: C) $mvg$

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Work

30. When is the work done by a force negative?

    • A) When the force acts in the same direction as displacement.
    • B) When the force acts perpendicular to displacement.
    • C) When the force opposes the displacement.
    • D) When there is no displacement.
      Answer: C) When the force opposes the displacement.

31. The work done in lifting a $10 \, \text{kg}$ object to a height of $2 \, \text{m}$ (take $g = 10 \, \text{m/s}^2$) is:

    • A) $20 \, \text{J}$
    • B) $100 \, \text{J}$
    • C) $200 \, \text{J}$
    • D) $400 \, \text{J}$
      Answer: C) $200 \, \text{J}$
      Solution: $W = mgh = 10 \times 10 \times 2 = 200 \, \text{J}$.

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Kinetic Energy

32. Doubling the velocity of a moving object will result in:

    • A) No change in kinetic energy.
    • B) Doubling its kinetic energy.
    • C) Tripling its kinetic energy.
    • D) Quadrupling its kinetic energy.
      Answer: D) Quadrupling its kinetic energy.
      Solution: $KE = \frac{1}{2}mv^2$. If $v$ is doubled, $KE \propto v^2$.

33. A bullet of mass $0.05 \, \text{kg}$ is fired at a velocity of $400 \, \text{m/s}$. What is its kinetic energy?

    • A) $2000 \, \text{J}$
    • B) $4000 \, \text{J}$
    • C) $8000 \, \text{J}$
    • D) $16000 \, \text{J}$
      Answer: C) $8000 \, \text{J}$
      Solution: $KE = \frac{1}{2}mv^2 = \frac{1}{2} \times 0.05 \times 400^2 = 8000 \, \text{J}$.

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Collisions

34. The loss in kinetic energy in a perfectly inelastic collision is maximum because:

    • A) Momentum is not conserved.
    • B) The two bodies stick together after collision.
    • C) The total energy is not conserved.
    • D) The collision is elastic.
      Answer: B) The two bodies stick together after collision.

35. Which type of collision conserves both kinetic energy and momentum?

    • A) Elastic collision
    • B) Inelastic collision
    • C) Perfectly inelastic collision
    • D) Partially elastic collision
      Answer: A) Elastic collision

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Miscellaneous

36. The energy consumption indicated in electricity bills is measured in:

    • A) Watts
    • B) Joules
    • C) Kilowatt-hours
    • D) Kilojoules
      Answer: C) Kilowatt-hours

37. A $1 \, \text{kg}$ object is thrown upwards with a velocity of $10 \, \text{m/s}$. At its highest point, its potential energy is:

    • A) $50 \, \text{J}$
    • B) $100 \, \text{J}$
    • C) $10 \, \text{J}$
    • D) $5 \, \text{J}$
      Answer: A) $50 \, \text{J}$
      Solution: $PE = KE_{\text{initial}} = \frac{1}{2}mv^2 = \frac{1}{2} \times 1 \times 10^2 = 50 \, \text{J}$.

38. If the work done on a system is positive, then the system’s energy:

    • A) Increases
    • B) Decreases
    • C) Remains unchanged
    • D) Becomes zero
      Answer: A) Increases

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• Quick Revision: MCQs cover key topics concisely, making them perfect for last-minute prep.
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Class 11 Physics MCQ Topics Covered

We’ve curated MCQs from the following critical chapters in the Class 11 Physics syllabus:

1. Physical World and Measurement

   • Example:
     Q: Which of the following is a fundamental unit in physics?
     a) Newton
     b) Kilogram
     c) Joule
     d) Watt
     Answer: b) Kilogram

2. Kinematics

   • Example:
     Q: A particle moves in a straight line with uniform acceleration. If its initial velocity is 5 m/s, acceleration is 2 m/s², and time is 3 seconds, what is the final velocity?
     a) 5 m/s
     b) 11 m/s
     c) 10 m/s
     d) 20 m/s
     Answer: d) 20 m/s

3. Laws of Motion

   • Example:
     Q: Newton’s first law is also known as:
     a) Law of Acceleration
     b) Law of Inertia
     c) Law of Gravitation
     d) None of these
     Answer: b) Law of Inertia

4. Work, Energy, and Power

   • Example:
     Q: The work done by a force is zero when the angle between force and displacement is:
     a) 0°
     b) 45°
     c) 90°
     d) 180°
     Answer: c) 90°

5. Gravitation

   • Example:
     Q: The value of acceleration due to gravity on the surface of Earth is approximately:
     a) 8.9 m/s²
     b) 9.8 m/s²
     c) 10.8 m/s²
     d) 11.8 m/s²
     Answer: b) 9.8 m/s²

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1. Understand Concepts Better: Solve real-life application-based problems.
2. Time Management: Learn to solve questions faster under exam conditions.
3. Boost Confidence: Build the confidence to face competitive exams.

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Pro Tips for Solving Physics MCQs

• Read the Question Carefully: Avoid making assumptions before fully reading.
• Practice Regularly: Consistency is key to mastering Physics MCQs.
• Understand Formulas: Memorize and apply the formulas correctly.
• Eliminate Wrong Options: Narrow down choices using logic.

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FAQs

1. Are these MCQs suitable for NEET or JEE aspirants?
   Yes, they are tailored to align with the syllabus of major competitive exams.
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   Stay tuned! A downloadable PDF link will be available soon.

Happy Learning! 🚀

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