Motion (Class 9 Science)

Motion is the change of position of an object with respect to time, and understanding its laws is fundamental to physics. This chapter covers distance, dis

Motion (Class 9 Science)

Motion is the change of position of an object with respect to time, and understanding its laws is fundamental to physics. This chapter covers distance, dis

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TL;DR: Motion is the change of position of an object with respect to time, and understanding its laws is fundamental to physics. This chapter covers distance…

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Motion is the change of position of an object with respect to time, and understanding its laws is fundamental to physics. This chapter covers distance, dis

Motion MCQs with Answers & Explanations

Q1. Which of the following is a scalar quantity?

  1. Velocity
  2. Speed ✓ (correct)
  3. Acceleration
  4. Displacement

Explanation: Speed is a scalar quantity that has magnitude only, while velocity, displacement, and acceleration are vectors.

Q2. The slope of a distance-time graph represents:

  1. Displacement
  2. Acceleration
  3. Speed ✓ (correct)
  4. Distance

Explanation: The slope of a distance-time graph gives the speed of the object.

Q3. If a car travels 100 m east and then 50 m west, its displacement is:

  1. 50 m west
  2. 150 m east
  3. 150 m west
  4. 50 m east ✓ (correct)

Explanation: Displacement is the straight-line distance with direction from initial to final position: 100 - 50 = 50 m east.

Q4. Acceleration is the rate of change of:

  1. Velocity ✓ (correct)
  2. Displacement
  3. Distance
  4. Speed

Explanation: Acceleration is defined as the rate of change of velocity with respect to time.

Q5. If an object moves with constant velocity, its acceleration is:

  1. Positive
  2. Zero ✓ (correct)
  3. Negative
  4. Infinite

Explanation: If velocity is constant, there is no change in velocity, so acceleration equals zero.

Q6. Newton's first law of motion states that:

  1. Action and reaction are equal
  2. Objects fall with constant acceleration
  3. An object in motion stays in motion unless acted upon by a force ✓ (correct)
  4. F = ma

Explanation: Newton's first law states that objects at rest remain at rest and objects in motion remain in motion unless external force acts.

Q7. Newton's second law can be expressed as:

  1. a = F/m
  2. v = u + at
  3. s = ut + 1/2 at^2
  4. F = ma ✓ (correct)

Explanation: Newton's second law states that Force equals mass times acceleration: F = ma.

Q8. An object is said to be in uniform motion when it:

  1. Travels equal distances in equal times ✓ (correct)
  2. Is at rest
  3. Has constant acceleration
  4. Travels in a circle

Explanation: Uniform motion occurs when an object travels equal distances in equal time intervals.

Q9. The SI unit of acceleration is:

  1. cm/s^2
  2. m/s^2 ✓ (correct)
  3. km/h
  4. m/s

Explanation: The SI unit of acceleration is meter per second squared (m/s^2).

Q10. If an object starts from rest and accelerates at 2 m/s^2 for 5 seconds, its final velocity is:

  1. 5 m/s
  2. 2 m/s
  3. 10 m/s ✓ (correct)
  4. 25 m/s

Explanation: Using v = u + at: v = 0 + (2 x 5) = 10 m/s.

Frequently Asked Questions

What is the difference between speed and velocity?

Speed is a scalar quantity (magnitude only) representing rate of motion, while velocity is a vector (magnitude and direction).

How do Newton's laws of motion apply to daily life?

Newton's laws explain phenomena like why we move forward when a car brakes suddenly (law 1) and why heavier objects need more force to move (law 2).

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