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CBSE 9th Physics Tutorials | Motion-Practice Questions for Examinations

September 22nd, 2015

Motion-Practice Questions for Examinations

Fill in the Blanks

1. If a car starts at rest and accelerates uniformly, the distance it travels is proportional to the ………. of the time it travels.
2. The speedometer of a car measures its…….. speed.
3. The slope of x-t graph gives the………… of motion.
4. Area below v-t graph is a measure of…………………
5. If a car is going northward and the driver jams on its brakes, the direction of its acceleration is………….
6. When an object is going in a circular path at constant speed, the direction of its acceleration is …….
7. A particle moves with a velocity v in a circle of radius r, then its angular velocity is equal to………….. and acts along the…………..
8. The ratio of angular speeds of minute hand and hour hand of watch is
9………… A truck traveling due north at 20 m/s turns left and travels at the same speed. Then the change in velocities……….
10. The magnitude of average velocity ………….equal to the average speed.

True / False

11. Magnitude of displacement can be equal to or lesser than distance.
12. If particle speed is constant, acceleration of the particle must be zero.
13. A body can have constant velocity and still have varying speed.
14. The movement of the earth about its axis is an example of uniform speed.
15. Unit of speed in S.I. system is cms-1.
16. A body falls freely from a height with uniform acceleration.
17. A particle is known to be at rest at time t = 0. Its acceleration at t = 0 must be zero.
18. In a journey, numerical value of displacement < distance.
19. If a body is moving on a curved path with constant speed, then its acceleration is perpendicular to the direction of motion.

Match the Columns

20. Match the situation given in column I with the possible curves in column II.
Column I Column II
(a) Particle moving with constant speed clip_image002
(b) Particle moving with increasing acceleration clip_image004
(c) Particle moving with constant negative acceleration clip_image006
(d) Particle moving with zero acceleration clip_image008

 

21. Match the items of column I against the items of column II.
Column I Column II
(a) Distance traveled by a uniformly accelerated body after time t. (p)   s = ut
(b) Distance traveled by a body moving with a

constant velocity

(q) image
(c) Distance covered by a uniformly accelerated

body in the nth second of its motion

(r)   image
(d) Speed (s) Displacement/Time taken
(e) Velocity (t) Distance traveled/Time taken

 

Multiple Choice Questions

Questions 22. If a body is moving at constant speed in a circular path, its

(a) Velocity is constant and its acceleration is zero
(b) Velocity and acceleration are both changing direction only
(c) Velocity and acceleration are both increasing
(d) Velocity is constant and acceleration is changing direction

Question 23. A graph is plotted showing the velocity of a car as a function of time. If the graph is a straight line, it means that

(a) the car started at rest
(b) acceleration was constant
(c) acceleration was increasing
(d) velocity was constant

Question 24. If a car is traveling north on a straight road and its brakes are applied, it will

(a) have no acceleration
(b) accelerate to the south
(c) accelerate to the north
(d) accelerate either east or west

Question 25. The acceleration of a car that speeds up from 12 meters per second to 30 meters per second in 15 seconds-

(a) 2.4 m/s2
(b) 1.2 m/s2
(c) 2m/s2
(d) 5.2 m/s2

Question 26. A car going at 24 meters per second passes a motorcycle at rest. As it passes, the motorcycle starts up, accelerating at 3.2 meters per second squared. If the motorcycle can keep up that acceleration, how long will it take for it to catch the car

(a) 12 s
(b) 14s
(c) 20s
(d) 18s

Question 27. Mohan takes 20 minutes to cover a distance of 3.2 kilometers due north on a bicycle, his velocity in kilometer/hour-

(a) 8.1
(b) 9.6
(c) 1.2
(d) 7.2

Question 28. A body moving along a straight line at 20 m/s undergoes an acceleration of-4 m/s2. After two seconds its speed will be

(a) -8 m/s
(b) 12 m/s
(c) 16 m/s
(d) 28 m/s

Question 29. A particle experiences constant acceleration for 20 seconds after starting from rest. If it travels a distance s( in the first 10 seconds and distance s2 in the next 10 seconds, then

(a) s2 = s1
(b) s2 = 2s1
(c) s2 = 3s1
(d) s2 = 4s1

Question 30 In which of the following cases, the object does not possess an acceleration or retardation when it moves in

(a) upward direction with decreasing speed
(b) downward direction with increasing speed
(c) with constant speed along circular path
(d) with constant speed along horizontal direction.
ANSWER KEY

1. Square              

2. instantaneous            

3. velocity               

4. displacement             

5. South                

6. centripetal                 

7. v/r, axis of ration 

8. 12                            

9. 20 clip_image022 m/sec. south-west                           

10. may or may not be     

11. True               

12. False                         

13. False                

14. True                          

15. False              

16. True                          

17. False                

18. True                          

19. False              

20. (a) clip_image024q, s(b) clip_image024[1]r (c) clip_image024[2]p (d) clip_image024[3]s        

21. (a) clip_image024[4](r);(b) clip_image024[5](p); (c) clip_image024[6](q); clip_image024[7](t); (e) clip_image024[8]s

22. (b)                   23. (b)                            24. (b)                        25.b)                            

26. (b)                   27. (b)                            28 (b)                         29.(c)

30. (d)             

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CBSE 9th Physics Tutorials | Motion: Short Answer Type Question with Answers

September 22nd, 2015

Motion: Short Answer Type Questions with Answers

Problem 1. The displacement-time graph for two particles A and B are straight lines inclined at angles of 30° and 60° with the time axis. What is the ratio of velocities of VA: VB ?

Solution.

image

Problem 2. An object is projected upwards with a velocity of 100 m/s. After what time will it strike the ground?

Solution

image

Problem 3. A car moving with a speed of 50 km/hr. can be stopped by brakes after at least 6m. If the same car is moving at a speed of 100 km/hr, find the minimum stopping distance.

Solution.

image

Problem 4. A particle starts from rest. Its acceleration (a) versus time (t) is as shown in the figure. What will be the maximum speed of the particle ?

image

 

Solution.

The area under acceleration time graph gives change in velocity. As acceleration is zero at the end of 11 sec.

image

Problem 5. Can an object maintain its motion in the same direction while reversing the direction of acceleration?

Solution.

Yes, reversing the direction of acceleration will produce retardation. Consequently the velocity

will start decreasing with time but the direction of motion will be maintained till the velocity is

reduced to zero and gets reversed.

Problem 6. It is the velocity and not the acceleration which decides the direction of motion of a body.” Justify this statement with the help of a suitable example.

Solution.

The direction of velocity is always in the direction of motion of the body, whereas the direction of acceleration may or may hot be is the direction of the motion of the body.

image

Hence, the velocity decides the direction of motion of the body.

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