Motion Class 9 Science Chapter 7 Important Questions, Download PDF

Important Questions Class 9 Science Chapter 7: Chapter 7 of Class 9 Science Motion explains the fundamental concepts of how objects move and the factors influencing their motion. Important questions, including class 9 motion important questions, cover topics like distance versus displacement, speed versus velocity, and the meaning of acceleration and deceleration. Students may need to solve problems to find average speed, read distance-time graphs, or use equations of motion for objects moving at a steady rate.

It is also important to understand concepts like frame of reference and different types of motion, such as uniform and non-uniform motion. By practicing these key questions from class 9 science chapter 7 important questions, students can strengthen their understanding of motion in the world around them.

Motion Class 9 Science Chapter 7 Important Questions PDF

Chapter 7 of Class 9 Science explains the basic ideas of how things move. It includes important questions on topics such as distance and displacement, speed and velocity, and acceleration and deceleration. These questions help students understand different types of motion like uniform and non-uniform motion. Practicing these important questions in PDF form can help students prepare well for exams and improve their grasp on the subject.

Download: Motion Class 9 Science Chapter 7 Important Questions PDF

Important Questions Class 9 Science Chapter 7 Motion 

MOST IMPORTANT QUESTIONS

1. Which of the following statements is correct?
   (A) Both speed and velocity are same.
   (B) Speed is a scalar quantity and velocity is a vector quantity.
   (C) Speed is a vector quantity and velocity is a scalar quantity.
   (D) None of these.
   Answer: (B)

2. What does the area of the velocity-time graph give?
   (A) Distance
   (B) Acceleration
   (C) Displacement
   (D) None of the above.
   Answer: (C)

3. When a body moves uniformly along a circle, then:
   (A) Its velocity changes but speed remains the same.
   (B) Its speed changes but velocity remains the same.
   (C) Both speed and velocity change.
   (D) Both speed and velocity remain same.
   Answer: (A)

4. Which of the following statements is correct?
   (A) Speed and distance are scalar, velocity and displacement are vector.
   (B) Speed and distance are vector, velocity and displacement are vector.
   (C) Speed and velocity are scalar, distance and displacement are vector.
   (D) Speed and velocity are vector, distance and displacement are scalar.
   Answer: (A)

5. If a moving body comes to rest, then its acceleration during its motion is:
   (A) Positive
   (B) Negative
   (C) Zero
   (D) All of these depending upon initial velocity.
   Answer: (B)

6. Under what condition(s) is the magnitude of average velocity of an object equal to its average speed?
   Answer: When the distance traveled by the object is equal to its displacement, the magnitude of the average velocity equals the average speed.

7. During an experiment, a signal from a spaceship reaches the ground station in five minutes. What was the distance of the spaceship from the ground station? The signal travels at the speed of light, 3 × 10^8 m/s.
   Solution:
   Distance = speed × time = (5 × 60 seconds) × (3 × 10^8 m/s) = 9 × 10^10 m = 9 × 10^7 km

8. A bus decreases its speed from 80 km/h to 60 km/h in 5 seconds. Find the acceleration of the bus.
   Solution:
   Initial speed (u) = 80 km/h = 22.22 m/s
   Final speed (v) = 60 km/h = 16.67 m/s
   Time (t) = 5 s
   Acceleration (a) = (v - u) / t = (16.67 - 22.22) / 5 = -1.11 m/s^2

9. A bus starting from rest moves with a uniform acceleration of 0.1 m/s^2 for 2 minutes. Find:
   (a) The speed acquired.
   (b) The distance traveled.
   Solution:
   (a) v = u + at = 0 + 0.1 × 120 = 12 m/s
   (b) s = ut + 0.5 at^2 = 0 + 0.5 × 0.1 × (120)^2 = 720 m

10. Calculate the acceleration of a body which starts from rest and travels 87.5 m in 5 sec.
    Solution:
    u = 0, s = 87.5 m, t = 5 sec
    Using s = ut + 0.5 at^2,
    87.5 = 0 + 0.5 × a × 25
    a = 2 × 87.5 / 25 = 7 m/s^2

11. A car travels at 40 km/hr for two hours and then at 60 km/hr for three hours. What is the average speed during the entire journey?
    Solution:
    s1 = 40 × 2 = 80 km
    s2 = 60 × 3 = 180 km
    Total distance = 260 km
    Total time = 5 hours
    Average speed = 260 / 5 = 52 km/hr

12. Derive the second equation of motion, s = ut + 0.5 at^2, numerically.
    Answer: By integrating the equations of motion and the graph, it can be shown that the second equation applies for uniformly accelerated motion.

13. A body moving at 12 m/s comes to rest after covering 18 m. Find its acceleration.
    Solution:
    v^2 = u^2 + 2as
    0 = (12)^2 + 2 × a × 18
    a = - 144 / 36 = -4 m/s^2

14. A farmer moves around the boundary of a square field of side 10 m in 40 seconds. What is the magnitude of displacement after 2 minutes 20 seconds?
    Solution:
    Distance covered in one round = 40 m
    Number of rounds in 140 seconds = 3 rounds = 120 m
    Remaining 20 seconds covers 20 m
    Total distance = 140 m
    Displacement = 10 × √2 ≈ 14.14 m

15. A train traveling at 90 km/h is brought to rest with a uniform acceleration of -0.5 m/s^2. Find the distance traveled before stopping.
    Solution:
    u = 25 m/s, v = 0, a = -0.5 m/s^2
    Using v^2 = u^2 + 2as,
    0 = (25)^2 + 2 × (-0.5) × s
    s = 625 m

16. The velocity-time graph of a runner shows total distance covered in 16 seconds as 130 m, with zero acceleration at t = 11 seconds.
    Answer: Distance = 130 m; acceleration at t = 11 s = zero.

17. Draw and interpret the position-time graph for uniform retardation.

(1) Position – time graph

(2) Velocity – time

18. Derive the third equation of motion, v^2 = u^2 + 2as, graphically.
Answer:

Through the area under the velocity-time graph, it can be shown that this relation holds for constant acceleration.

19. Abdul, while driving to school, computes the average speed for his trip to be 20 km h–1. On his return trip along the same route, there is less traffic and the average speed is 40 km h–1. What is the average speed for Abdul's trip?

Answer:  Total distance = 2x, total time = (x/20) + (x/40) = 3x/40
Average speed = (Total distance) / (Total time) = (2x) / (3x/40) = 80/3 ≈ 26.67 km/h

20. Assertion: Motion with uniform velocity is always along a straight line path.

Reason: In uniform velocity, speed is the magnitude of the velocity and is equal to the instantaneous velocity.

(A) Both assertion and reason are true and reason is the correct explanation of assertion.

(B) Both assertion and reason are true but reason is not the correct explanation of assertion. Assertion is true but reason is false.

Both Assertion and Reason are false.

Benefits of Important Questions Class 9 Science Chapter 7

• Enhanced Understanding : These questions help clarify important concepts related to motion, speed, velocity, and acceleration ensuring students grasp fundamental principles.
• Exam Preparation : Familiarity with important questions boosts confidence and readiness for tests, as students can anticipate similar questions in their exams.
• Time Management : Practicing these questions allows students to learn how to manage their time effectively during exams, ensuring they can complete all questions within the allotted time.
• Self-Assessment : Important questions enable students to assess their understanding and identify areas needing further review or practice.

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