Motion Class 9 PhysicsSource - S Chand
Multiple
Choice Questions (MCQs)
42. A
particle is moving in a circular path of radius r. The displacement after half
a circle would be :
(a) 0 (b)
rtr (c) 2r (4) 2itr
43. The
numerical ratio of displacement to distance for a moving object is :
(a) always
less than 1 (b) equal to 1 or more than 1 (c) always more than 1 (d) equal to 1
or less than 1
44. A boy is
sitting on a merry-go-round which is moving with a constant speed of 10 m s-1.
This means that the boy is :
(a) at rest (1)
moving with no acceleration (c) in accelerated motion (d) moving with uniform velocity
45. In which of the following cases of motion,
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 on circular road (c) if
the pendulum is moving to and fro (d) if a planet is moving around the sun
46. The
speed of a moving object is determined to be 0.06 m/s. This speed is equal to :
(a) 2.16
km/h (b) 1.08 km/h (c) 0.216 km/h (h) 0.0216 km/h
47. A freely
falling object travels 4.9 m in 1st second, 14.7 m in 2nd second, 24.5 m in 3rd
second, and so on. This data shows that the motion of a freely falling object
is a case of :
(a) uniform
motion
(b) uniform
acceleration
(c) no
acceleration
(d) uniform
velocity
48. When a
car runs on a circular track with a uniform speed, its velocity is said to be
changing. This is because:
(a) the car
has a uniform acceleration
(b) the
direction of car varies continuously
(c) the car
travels unequal distances in equal time intervals
(d) the car
travels equal distances in unequal time intervals
49. Which of
the following statement is correct regarding velocity and speed of a moving
body?
(a) velocity of a moving body is always higher
than its speed
(b) speed of
a moving body is always higher than its velocity
(c) speed of
a moving body is its velocity in a given direction
(d) velocity
of a moving body is its speed in a given direction
50. Which of
the following can sometimes be 'zero' for a moving body?
(i) average
velocity (ii) distance travelled (iii) average speed (iv) displacement
(a) only
(i) (b) (i) and (ii) (c) (i) and (iv) (d)
only (iv)
51. When a
car driver travelling at a speed of 10 m/s applies brakes and brings the car to
rest in 20 s, then retardation will be :
(a) + 2 in/s2
(b) — 2 m/s2 (c) — 0.5 in/s2 (d) + 0.5 m/s2
52. Which of
the following could not be a unit of speed?
(a) km/h (b)
s/m (c) m/s (d) mm s-1
53. One of
the following is not a vector quantity. This one is:
(a)
displacement (b) speed (c) acceleration (d) velocity
54. Which of
the following could not be a unit of acceleration?
(a) km/s2
(b) cm s-2 (c) km/s (d) m/s2
Short Answer
Type Questions
1. Is
displacement a scalar quantity?
2. State
whether distance is a scalar or a vector quantity.
3. Change
the speed of 6 m/s into km/h.
4. What name
is given to the speed in a specified direction?
5. Give two
examples of bodies having non-uniform motion.
6. Name the physical quantity obtained by
dividing 'Distance travelled' by 'Time taken' to travel that distance.
7. What do
the following measure in a car? (a) Speedometer (b) Odometer
8. Name the
physical quantity which gives us an idea of how slow or fast a body is moving.
9. Under
what conditions can a body travel a certain distance and yet its resultant
displacement be zero ?
10. In
addition to speed, what else should we know to predict the position of a moving
body ?
11. When is
a body said to have uniform velocity ?
12. Under
which condition is the magnitude of average velocity equal to average speed ?
13. Which of
the two can be zero under certain conditions : average speed of a moving body
or average velocity of a moving body ?
14. Give one
example of a situation in which a body has a certain average speed but its
average velocity is zero.
15. What is
the acceleration of a body moving with uniform velocity ?
16. What is
the other name of negative acceleration ?
17. Name the
physical quantity whose SI unit is : (a) m/s (13) m/s2
18. What
type of motion is exhibited by a freely falling body ?
19. What is
the SI unit of retardation ?
20. Fill in
the following blanks with suitable words :
(a)
Displacement is a ……………. quantity whereas distance is a ……………. quantity.
(b) The
physical quantity which gives both, the speed and direction of motion of a body
is its ………………
(c) A
motorcycle has a steady ……………… of 3 m/s2. This means that every …………….. its
……………. Increases by ………………..
(d) Velocity
is the rate of change of ………………. It is measured in ……………….
(e) Acceleration
is the rate of change of ……………….. It is measured in ……………….
Short Answer
Type Questions
21. What
type of motion, uniform or non-uniform, is exhibited by a freely falling body ?
Give reason for y answer.
22. State
whether speed is a scalar or a vector quantity. Give reason for your choice.
23. Bus X
travels a distance of 360 km in 5 hours whereas bus Y travels a distance of 476
km in 7 hours. Why bus travels faster ?
24. Arrange
the following speeds in increasing order (keeping the least speed first):
(i) An
athlete running with a speed of 10 m/s.
(ii) A
bicycle moving with a speed of 200 m/min.
(iii) A
scooter moving with a speed of 30 km/h. 25.
(a) Write
the formula for acceleration. Give the meaning of each symbol which occurs in
it.
(b) A train starting from Railway Station
attains, a speed of 21 rn/s in one minute. Find its acceleration.
26. (a) What
term is used to denote the change of velocity with time ?
(b) Give one
word which means the same as 'moving with a negative acceleration'.
(c) The
displacement of a moving object in a given interval of time is zero. Would the
distance travelled the object also be zero ? Give reason for your answer.
27. A snail
covers a distance of 100 metres in 50 hours. Calculate the average speed of
snail in km/h.
28. A
tortoise moves a distance of 100 metres in 15 minutes. What is the average
speed of tortoise in km/h ?
29. If a
sprinter runs a distance of 100 metres in 9.83 seconds, calculate his average
speed in km/h.
30. A
motorcyclist drives from place A to B with a uniform speed of 30 km h-1 and returns
from place 13 to A with a uniform speed of 20 km h-1. Find his average speed.
31. A
motorcyclist starts from rest and reaches a speed of 6 m/s after travelling
with uniform acceleration for 3 s. What is his acceleration ?
32. An
aircraft travelling at 600 km/h accelerates steadily at 10 km/h per second.
Taking the speed of sound as 1100 km/h at the aircraft's altitude, how long
will it take to reach the 'sound barrier' ?
33. If a bus
travelling at 20 m/s is subjected to a steady deceleration of 5 m/s2, how long
will it take to come to rest ?
'Long Answer
Type Questions
34. (a) What
is the difference between 'distance travelled' by a body and its 'displacement'
? Explain with the help of a diagram.
(b) An ant
travels a distance of 8 cm from P to Q and then moves a distance of 6 cm at
right angles to PQ. Find its resultant displacement.
35. Define
motion. What do you understand by the terms 'uniform motion' and 'non-uniform
motion' ? Explain with examples.
36. (a)
Define speed. What is the SI unit of speed ?
(b) What is
meant by
(i) average
speed, and (ii) uniform speed ?
37. (a)
Define velocity. What is the SI unit of velocity ?
(b) What is
the difference between speed and velocity ?
(c) Convert
a speed of 54 km/h into m/s.
38. (a) What
is meant by the term 'acceleration' ? State the SI unit of acceleration.
(b) Define
the term 'uniform acceleration'. Give one example of a uniformly accelerated
motion.
39. The
distance between Delhi and Agra is 200 km. A train travels the first 100
kilihaole t a iosptmley ?of 50 km/h. How fast must the train travel the next
100 km, so as to average 70 km/h for the whole
40. A train
travels the first 15 km at a uniform speed of 30 km/h; the next 75 km at a
uniform speed of 50 km/h; and the last 10 km at a uniform speed of 20 km/h.
Calculate the average speed for the entire train journey.
41. A car is
moving along a straight road at a steady speed. It travels 150 m in 5 seconds :
(a) What is
its average speed ?
(b) How far
does it travel in 1 second ?
(c) How far
does it travel in 6 seconds ?
(d) How long
does it take to travel 240 m ?
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