NCERT Class 9 Physics Numerical Questions for Motion Board Sample Problems
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Question 1. A train accelerates from 36 km/h to 541 km/h in 10 sec.
(j) Acceleration
(ii) The distance travelled by car.
Answer
a) Acceleration is given by
So
b) Distance is given by
S
So s = 125m
Question 2. A body whose speed is constant
(a) Must be accelerated
(b) Might be accelerated
(c) Has a constant velocity
(d) Cannot be accelerated.
Answer
Might be accelerated
Question 3. A truck traveling at 54 km/h is slow down to 36 km/h in 10 sec. Find the retardation of
Answer
Acceleration is given by
So a =-. 5 m/
Negative sign implies retardation
Question 4. A particle is moving in a circle of diameter 20m. What is its distance and as per the table given below
S. No | Rounds | Displacement | Distance |
1 | 1 | ||
2 | 1.5 | ||
3 | 2 | ||
4 | 2.5 |
Answer:
S. No | Rounds | Displacement | Distance |
1 | 1 | 0 | |
2 | 1.5 | 20m | |
3 | 2 | 0 | |
4 | 2.5 | 20m |
Question 5. A scooter travelling at 10 m/s speed up to 20 m/s in 4 sec. Find the acceleration of train.
Answer
Acceleration is given by
So a = 1.25 m/
Question 6. A train starts from rest and accelerate uniformly at the rate of 5 m/sŐ for 5 sec.
Calculate the velocity of train in 5 sec.
Answer
25m/s
Question 7. A object moves with uniform positive acceleration. Its velocity-time graph will be
(a) A straight line parallel to the time axis
(b) A straight line inclined at an obtuse angle to the time axis
(c) A straight line inclined at an acute angle to the time axis
(d) None of these.
Solutions (c)
Question 8. The maximum speed of a train is 90 km/h. It takes 10 hours to cover a distance of 500 km.
Find the ratio of its average speed to maximum speed?
Solution
Average speed km/hr
Ratio of average speed to maximum speed = 50: 90 = 5: 9
Question 9. A car start from rest and acquire a velocity of 54 km/h in 2 sec. Find (i) the acceleration (ii) distance travelled by car assume motion of car is uniform?
Solution
a) Acceleration is given by
So a = 7.5 m/
b) Distance is given by
Question 10. An object dropped from a cliff falls with a constant acceleration of 10 m/. Find its speed 5 s after it was dropped.
Solution:
m/s
Question 11. A ball is thrown upwards and it goes to the height loo m and comes down
1) What is the net displacement?
2) What is the net distance?
Solution:
As it comes down to the initial point
Net displacement is zero
Net distance = 200 m
Practice Questions
Question 12. two cars A and B race each other. The Car A ran tar 2 min at a speed of 7.5 km/h, slept for
56 min and again ran for 2 min at a speed of 7.5 km/h. find the average speed of the car A in the race.
Question 13. Anand leaves his house at 8.30 a. m. for his school. The school is 2 km away and classes start at 9.00 a. m. If he walks at a speed of 3 km/h for the first kilometer, at what speed should he walk the second kilometer to reach just in time?
Question 14. An object moves along a straight line with an acceleration of 2 m/. If its initial speed is 10 m/s, what will be its speed 2 s later?
Question 15. A bullet hits a Sand box with a velocity of 20 m/s and penetrates it up to a distance of 6 cm.
Find the deceleration of the bullet in the sand box.
Question 16. A particle experiences constant acceleration for 20 seconds after starting from rest. If it travels a distance in the first 10 seconds and distance in the next 10 seconds then,
(a)
(b)
(c)
(d)