NEW LEARNET EDUCATION
Chapter 8 – Motion (Multiple Choice Questions)
PART -1
1. A particle is moving in a circular path of radius r. The displacement after half a circle would be:
(a) Zero
(b) π r
(c) 2 r
(d) 2π r
Soln:
Answer is (c) 2 r
Explanation:
After half revolution
Distance travelled = X circumference= πr
Path length
Displacement = Final position- Initial Position
It comes out to be the diameter of the circle = 2R.
2. A body is thrown vertically upward with velocity u, the greatest height h to which it will rise is,
(a) u/g
(b) u2/2g
(c) u2/g
(d) u/2g
Soln:
Answer is (b) u2/2g
Explanation:
V2= u2+2 as
here v = 0
a = -g
s = H
0 = u² -2gH
H = u²/2g
3. The numerical ratio of displacement to distance for a moving object is
(a) always less than 1
(b) always equal to 1
(c) always more than 1
(d) equal or less than 1
Soln:
Answer is (d) equal or less than 1
Explanation:
The shortest distance between the initial and the endpoint is called displacement. Distance is the total path length.
Displacement is vector and it may be positive or negative whereas Distance is scalar and it can never be negative.
The distance can be equal or greater than displacement which means the ratio of displacement to distance is always equal to or less than 1.
4. If the displacement of an object is proportional to square of time, then the object moves with
(a) uniform velocity
(b) uniform acceleration
(c) increasing acceleration
(d) decreasing acceleration
Soln:
Answer is (b) uniform acceleration
Explanation:
Velocity is measured in distance /second and acceleration is measured in Distance/ second2. Hence Uniform acceleration is the right answer.
5. From the given v – t graph (Fig. 8.1), it can be inferred that the object is
(a) in uniform motion
(b) at rest
(c) in non-uniform motion
(d) moving with uniform acceleration
Soln:
Answer is (a) in uniform motion
Explanation:
From the above-given graph, it is clear that velocity of the object remains constant throughout hence the object is in uniform motion.
6. Suppose a boy is enjoying a ride on a merry-go-round which is moving with a constant speed of 10 m/s. It implies that the boy is
(a) at rest
(b) moving with no acceleration
(c) in accelerated motion
(d) moving with uniform velocity
Soln:
Answer is (c) in accelerated motion
Explanation:
Boy is moving in a circular motion and circular motion is an accelerated motion hence C) is right answer.
7. Area under a v – t graph represents a physical quantity which has the unit
(a) m2
(b) m
(c) m3
(d) m s–1
Soln:
Answer is (b) m
Explanation:
The area given in the graph represents Displacement and its unit is meter. Hence the answer is (b) m
8. Four cars A, B, C and D are moving on a levelled road. Their distance versus time graphs are shown in Fig. 8.2. Choose the correct statement
(a) Car A is faster than car D.
(b) Car B is the slowest.
(c) Car D is faster than car C.
(d) Car C is the slowest.
Soln:
Answer is (b) Car B is the slowest.
Explanation:
Graph shows that Car B covers less distance in a given time than A, C and D cars hence it is the slowest.
9. Which of the following figures (Fig. 8.3) represents uniform motion of a moving object correctly?
Soln:
Answer is (a)
Explanation:
Distance in graph a) is uniformly increasing with time hence it represents uniform motion.
10. Slope of a velocity – time graph gives
(a) the distance
(b) the displacement
(c) the acceleration
(d) the speed
Soln:
Answer is (c) the acceleration
11. In which of the following cases of motions, the distance moved and the magnitude of displacement are equal?
(a) If the car is moving on straight road
(b) If the car is moving in circular path
(c) The pendulum is moving to and fro
(d) The earth is revolving around the Sun
Soln:
Answer is (a) If the car is moving on a straight road
Explanation:
In other cases given here displace can be less than distance hence option (a) If the car is moving on a straight road is the right answer.
Short Answer Questions
12. The displacement of a moving object in a given interval of time is zero. Would the distance travelled by the object also be zero? Justify your answer.
Soln:
Displacement zero does not mean zero distance. The distance can be zero when moving an object back to the place it started. Displacement is either equal or less than distance but the distance is always greater than one and it cannot be a negative value.
13. How will the equations of motion for an object moving with a uniform velocity change?
Soln:
If object is moving with a uniform velocity then v=µ and a=0. In this scenario equation for distance is given below.
S= ut and V2– µ2=0
14. A girl walks along a straight path to drop a letter in the letterbox and comes back to her initial position. Her displacement–time graph is shown in Fig.8.4. Plot a velocity-time graph for the same.
Soln:
15. A car starts from rest and moves along the x-axis with constant acceleration of 5 m/s2 for 8 seconds. If it then continues with constant velocity, what distance will the car cover in 12 seconds since it started from the rest?
Soln:
Car Starts from rest hence Initial velocity u=o acceleration a=5 m/s2 and time t=8s
v = u+at
v = 0+5×8
v = 40ms-1
From second equation
s = ut +
s = 0x8 +
s =
s =
s = 5×32=160 is the distance coveed in 8 seconds.
The total distance covered in 12 seconds, therefore, is 160+160=320m
16. A motorcyclist drives from A to B with a uniform speed of 30 km/h and returns back with a speed of 20 km h–1. Find its average speed.
Soln:
Let the distance from A to B is D kms.
Distance for the entire journey is 2D kms.
Time taken to go from A to B is D/30 hr and that of B to A is D/20 hr. So, total time taken T is
T = (D/30) + (D/20). By solving, we will get,
T = D/12 hrs.
Average speed = Total distance/Total time.
Av.speed = 2D ÷ D/12
=> 2D x 12/D = 24 km/h.
Hence Average speed of the motorcycle is 24 km/h.
17. The velocity-time graph (Fig. 8.5) shows the motion of a cyclist. Find (i) its acceleration (ii) its velocity and (iii) the distance covered by the cyclist in 15 seconds
Soln:
(i) As velocity is constant, acceleration is 0 m/s2
(ii) Here Velocity is constant hence v=20m/s
(iii) s = v x t
= 20 x 15
= 300 m
18. Draw a velocity versus time graph of a stone thrown vertically upwards and then coming downwards after attaining the maximum height.
Soln:
The velocity versus time graph of a stone thrown upwards vertically is as given below:
19. An object is dropped from rest at a height of 150 m and simultaneously another object is dropped from rest at a height 100 m. What is the difference in their heights after 2 s if both the objects drop with same accelerations? How does the difference in heights vary with time?
Soln:
When two objects fall with the same acceleration simultaneously, after 2 seconds the difference in their heights will not change and it remains 50 m.
Therefore the height of the first object after 2 seconds is 130 m.
In the same way, the height of the second object is
Therefore, the height of the second object after 2 seconds is 80 m.
So, the difference is the same, i.e. 50 m.
This concludes that the difference in height of the two objects does not depend on time and will always be same.
20. An object starting from rest travels 20 m in first 2 s and 160 m in next 4 s. What will be the velocity after 7 s from the start.
Soln:
Here Object starts from rest hence initial velocity u=0 t =2s and s=20 m
According to Second equation of motion s= ut+at2
S = 0+
20 = 2+
= 20/2
a = 10m/s
According to first equation of motion velocity after 7 s from the start
V = u+at
V = 0+10×7
V = 70m/s
21. Using following data, draw time – displacement graph for a moving object:
| Time(s) | 0 | 2 | 4 | 6 | 8 | 10 | 12 | 14 | 16 |
| Displacement(m) | 0 | 2 | 4 | 4 | 4 | 6 | 4 | 2 | 0 |
Use this graph to find average velocity for first 4 s, for next 4 s and for last 6 s.
Soln
Average velocity for the first 4s =
Average velocity of next 4 s = V =
Average velocity for last 6 s =
22. An electron moving with a velocity of 5 × 104 m/s enters into a uniform electric field and acquires a uniform acceleration of 104 ms-2 in the direction of its initial motion.
(i) Calculate the time in which the electron would acquire a velocity double of its initial velocity.
(ii) How much distance the electron would cover in this time?
Soln:
Given initial velocity, u = 5 × 104 m/s and acceleration, a = 104ms-2
(i) final velocity = v = 2 u = 2 × 5 ×104 m/s =10 × 104 m/s
To find t, use v = at or t = u – u / a = (5 × 104)/104
=5s
(ii) Using s = ut +
= 25 ×104 + 25 /2 ×104
= 37.5×104 m
23. Obtain a relation for the distance travelled by an object moving with a uniform acceleration in the interval between 4th and 5th seconds.
Soln:
a = dv/dt
Assume that air resistance is nil.
We can directly contain it by using Newton’s equations of motion or from the below-mentioned method:
Thus area under the v-t curve and the x-axis where the slope of the curve is the instantaneous acceleration.
In this case acceleration, g is constant and due to free-fall condition, the initial velocity is zero. Therefore the v-t curve is a straight line with a slope equal to g equal to 9.81 m/s passing through the origin.
On dividing the total area under the curve into the interval of unit seconds, then we initially obtain a triangle followed by trapeziums of increasing height.
The ratio of the area of the first triangle to second triangle to the third triangle is equal to the ratio of displacement in first, second and third second. We get ratio equal to 1:3:5:7:9… and so on.
For 4th & 5th second it is 7:9.
24. Two stones are thrown vertically upwards simultaneously with their initial velocities u1 and u2 respectively. Prove that the heights reached by them would be in the ratio of u1² :u2²
( Assume upward acceleration is –g and downward acceleration to be +g ).
Soln:
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PART - 2
Question 1.
A particle is moving in a circular path of radius r. The displacement after half a circle would be:
(a) Zero
(b) πr
(c) 2r
(d) 2πr
Answer
Answer: (c) 2r
Question 2.
A body is thrown vertically upward with velocity u, the greatest height h to which it will rise is,
(a) ulg
(b) u2l2g
(c) u2lg
(d) ul2g
Answer
Answer: (b) u2l2g
Question 3.
The numerical ratio of displacement to distance for a moving object is
(a) always less than 1
(b) always equal to 1
(c) always more than 1
(d) equal or less than 1
Answer
Answer: (d) equal or less than 1
Question 4.
If the displacement of an object is proportional to square of time, then the object moves with
(a) uniform velocity
(b) uniform acceleration
(c) increasing acceleration
(d) decreasing acceleration
Answer
Answer: (b) uniform acceleration
Question 5.
From the given υ – t graph, it can be inferred that the object is
MCQ Questions for Class 9 Science Chapter 8 Motion with Answers 1
(a) in uniform motion
(b) at rest
(c) in non-uniform motion
(d) moving with uniform acceleration
Answer
Answer: (a) in uniform motion
Question 6.
Suppose a boy is enjoying a ride on a merry-go-round which is moving with a constant speed of 10 ms-1 It implies that the boy is
(a) at rest
(b) moving with no acceleration
(c) in accelerated motion
(d) moving with uniform velocity
Answer
Answer: (c) in accelerated motion
Question 7.
Area under a υ -1 graph represents a physical quantity which has the unit
(а) m2
(b) m
(c) m3
(d) ms-1
Answer
Answer: (b) m
Question 8.
Four cars A, B, C and D are moving on a levelled road. Their distance versus time graphs are shown in the adjacent figure. Choose the correct statement.
MCQ Questions for Class 9 Science Chapter 8 Motion with Answers 2
(a) Car A is faster than car D.
(b) Car B is the slowest.
(c) Car D is faster than car C.
(d) Car C is the slowest.
Answer
Answer: (b) Car B is the slowest.
Question 9.
Which of the following figures correctly represents uniform motion of a moving object?
MCQ Questions for Class 9 Science Chapter 8 Motion with Answers 3
Answer
Answer: (a)
Question 10.
Slope of a velocity-time graph gives
(a) the distance
(b) the displacement
(c) the acceleration
(d) the speed
Answer
Answer: (c) the acceleration
Question 11.
In which of the following cases of motions, the distance moved and the magnitude of displacement are equal?
(a) If the car is moving on a straight road
(b) If the car is moving in Circular path
(c) The pendulum is moving to and fro
(d) The earth is revolving around the sun.
Answer
Answer: (a) If the car is moving on a straight road
Question 12.
A boy goes from A to B with a velocity of 20 m/min and comes back from B to A with a velocity of 30 m/min. The average velocity of the boy during the whole journey is
(a) 24 m/min
(b) 25 m/s
(c) Zero
(d) 20 m/min
Answer
Answer: (a) 24 m/min
Question 13.
Velocity-time graph of an object is given below. The object has
MCQ Questions for Class 9 Science Chapter 8 Motion with Answers 4
(a) Uniform velocity
(b) Uniform speed
(c) Uniform retardation
(d) Variable acceleration
Answer
Answer: (c) Uniform retardation
Question 14.
Which one of the following graphs shows the object to be stationary?
MCQ Questions for Class 9 Science Chapter 8 Motion with Answers 5
Answer
Answer: (b)
Question 15.
A body is projected vertically upward from the ground. Taking vertical upward direction as positive and point of projection as origin, the sign of displacement of the body from the origin when it is at height h during upward and downward journey will be
(a) Positive, positive
(b) Positive, negative
(c) Negative, negative
(d) Negative, positive
Answer
Answer: (a) Positive, positive
Question 16.
According to the given velocity-time graph, the object
MCQ Questions for Class 9 Science Chapter 8 Motion with Answers 6
(a) is moving with uniform velocity
(b) has some initial velocity
(c) is moving uniformly with some initial velocity
(d) is at rest
Answer
Answer: (b) has some initial velocity
Question 17.
The ratio of speed to the magnitude of velocity when the body is moving in one direction is
(a) Less than one
(b) Greater than one
(c) Equal to one
(d) Greater than or equal to one
Answer
Answer: (c) Equal to one
Question 18.
A car is moving along a straight road with uniform velocity. It is shown in the graph.
MCQ Questions for Class 9 Science Chapter 8 Motion with Answers 7
Answer
Question 19.
Which of the following situations is possible?
(a) An object can have acceleration, but constant velocity.
(b) The velocity of an object may be zero but acceleration is not zero.
(c) Distance and the magnitude of displacement are equal in circular motion.
(d) Average speed and the magnitude of average velocity are always equal in circular motion.
Answer
Answer: (b) The velocity of an object may be zero but acceleration is not zero.
Question 20.
Which of the following graphs is not possible?
MCQ Questions for Class 9 Science Chapter 8 Motion with Answers 8
Answer
Answer: (b)
Fill in the blanks:
1. The total path length travelled by a body in a given interval of time is called …………….
Answer
Answer: distance
2. A body moving in a straight line has a uniform motion if it travels ……………. distance in …………… intervals of time.
Answer
Answer: equal, equal
3. Velocity is defined as ……………. per unit time.
Answer
Answer: displacement
4. Speed is scalar quantity and velocity is ……………… quantity.
Answer
5. If speed of a body is continuously decreasing, the body is said to ……………
Answer
Answer: retarding
6. Acceleration is vector quantity and its SI unit is ……………..
Answer
Answer: ms-2
7. A physical quantity that has magnitude as well as …………… is called vector quantity.
Answer
Answer: direction
8. The slope of velocity-time graph gives …………….. and the slope of displacement-time graph gives ……………..
Answer
Answer: acceleration, velocity
III. Match the following columns
Column I Column II
(a) Straight line parallel to time axis in velocity-time graph (i) Scalar quantity
(b) Distance (ii) Body at rest
(c) Displacement (iii) Motion of object in circular path with uniform speed
(d) Straight line parallel to time axis in position time graph (iv) Body in uniform motion
(e) Uniform circular motion (v) Rate of change of velocity with respect to time
(f) Slope of velocity-time graph gives (vi) Shortest distance between initial and final position
(g) Acceleration (vii) Acceleration
Answer
Answer:
Column I Column II
(a) Straight line parallel to time axis in velocity-time graph (i) Scalar quantity
(b) Distance (ii) Body at rest
(c) Displacement (iii) Motion of object in circular path with uniform speed
(d) Straight line parallel to time axis in position time graph (iv) Body in uniform motion
(e) Uniform circular motion (v) Rate of change of velocity with respect to time
(f) Slope of velocity-time graph gives (vi) Shortest distance between initial and final position
(g) Acceleration (vii) Acceleration
Complete the crossword given below:
MCQ Questions for Class 9 Science Chapter 8 Motion with Answers 9
Across:
3. Displacement per unit time
4. Rate of change of velocity
5. A physical quantity which is described completely by its magnitude only
6. If a body travels equal distance in equal intervals of time in straight line then motion is
Down:
1. Motion of body in circular path
2. Area of speed-time graph gives
7. SI unit of distance and displacement
Answer
Answer:
Across:
3. Velocity
4. Acceleration
5. Scalar quantity
6. Uniform motion
Down:
1. Circular motion
2. Distance
7. Metre
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(a) 60 km/h
(b) 20 km/h
(c) 30 km/h
(d) 10 km/h
► (b) 20 km/h
(a) Distance – time graph
(b) Velocity – time graph for non-uniform acceleration
(c) Displacement time graph
(d) Velocity – time graph for uniform acceleration
► (d) Velocity – time graph for uniform acceleration
► (a) 19 m
4. Which of the following is a correct measure of velocity?
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