CBSE Questions for Class 9 Physics Motion Quiz 7 - MCQExams.com

Acceleration is defined as 
  • the rate of change of velocity with respect to time.
  • the rate of change of position with respect to time.
  • the rate of change of momentum with respect to time.
  • None of the above
The rate of change of velocity of an object with respect to time is called ..........
  • Momentum
  • Displacement
  • Acceleration
  • Impulse
What does the graph represents:
270960_695fc1ef66274861af555967a6a388ad.png
  • uniform speed
  • non-uniform speed
  • both A and B
  • none of these
A person walks along an east-west street and a graph of his displacement from home is shown in figure. His average velocity  for the whole time interval is 
283406.png
  • $$0\;ms^{-1}$$
  • $$23\;ms^{-1}$$
  • $$8.4\;ms^{-1}$$
  • None of above
The cheetah is the fastest land animal that can attain a maximum speed of $$112~ km/h$$. Express this speed in $$m/s$$.
  • $$31 ~m/s$$ (approx.)
  • $$30 ~m/s$$ (approx.)
  • $$32 ~m/s$$ (approx.)
  • $$29 ~m/s$$ (approx.)
What distance was covered by the bus at 9.45 a.m.?
  • 70 m
  • 80 m
  • 90
  • Can't be determined
Figure shows the position of a particle moving on the x-axis as a function time
283435_552a78d5c5b0491ba1cbbb04232a2c01.png
  • the particle has come to rest 6 times
  • the maximum speed is at t=6 s
  • the velocity remains positive for t=0 to t=6 s
  • the average velocity for the total period show in negative
A bullet loses $$\dfrac{1}{20}$$ of its velocity in passing through a plank. What is the least number of planks required to stop the bullet?
  • 9
  • 10
  • 11
  • 12
If an object is moving eastward and slowing down, then the direction of its velocity vector is 
  • Eastward
  • Westward
  • Neither eastward nor westward
  • Not enough information to tell
A student determined to test the law of gravity for himself walks off a sky scraper 320 m high with a stopwatch in hand and starts his free fall (zero initial velocity). 5 second later, superman arrives at the scene and dives off the roof to save the student. What must be the maximum height of the skyscraper so that even superman cannot save him.
  • 65 m
  • 85 m
  • 125 m
  • 145 m
If a train travelling at $$72$$  km/h is to be brought to rest at a distance of $$200$$ m then its retardation should be :
  • $$20\  m/s^{2}$$
  • $$2 \ s^{2}$$
  • $$10 \ m/s^{2}$$
  • $$1 \ m/s^{2}$$
Figure shows the position time graph of a particle moving on the x-axis.
292925.png
  • The particle is continuously going in positive x direction
  • Area under x - t curve shows the displacement of particle
  • The velocity increases up to a time $$t_0$$, and then becomes constant.
  • The particle moves at a constant velocity up to a time $$t_0$$, and then stops.
Which of the following four statement is false?
  • A body can have zero velocity and still be accelerated.
  • A body can have a constant velocity and still have a varying speed.
  • A body can have a constant speed and still have a varying velocity.
  • The direction of the velocity of a body can change when its acceleration is constant.
Which one of the following is travelling with the fastest speed?
  • An athlete running with a speed of 10 m/s
  • A bicycle moving with a speed of 200 m/min
  • A tortoise covering 100 metres in 15 minutes
  • A motorcycle moving with a speed one km/h
A stone is dropped from a height of 20 m. How long will it take to reach the ground? ($$ {g=10 m/s^2}$$ ).
  • 2 s
  • 0.5 s
  • 4 s
  • 1 s
A truck increases its speed from $$10km/h$$ to $$50 km/h$$ in $$20$$ seconds. Its acceleration is:
  • $$0.55 m/s^2$$
  • $$2.55 m/s^2$$
  • $$0.75 m/s^2$$
  • $$8.65 m/s^2$$
A and B are thrown vertically upward with velocity, 5 m/s and 10 m/s respectively $$(g = 10\ m/s^{2})$$. Find separation between them after one second.
  • 5 m
  • 12 m
  • 3 m
  • 7 m
A moving bus is brought to rest within 30 seconds by applying brakes. What is its initial velocity, if the retardation due to brakes is 2 $$ms^{-2}$$?
  • $$60\ ms^{-1}$$
  • $$15\ ms^{-1}$$
  • $$40\ ms^{-1}$$
  • $$30\ ms^{-1}$$
A car is moving with a uniform velocity of 40 km h$$^{-1}$$ in straight line. Its acceleration after 1 hour is:
  • 40 km h$$^{-1}$$
  • 20 km h$$^{-1}$$
  • 30 km h$$^{-1}$$
  • zero
A ball starts rolling on a horizontal surface with an initial velocity of $$1 \ m/s.$$ Due to friction, its velocity decreases at the rate of $${0.1 m/s^2}$$. How much time will it take for the ball to stop?
  • 1 s
  • 100 s
  • 10 s
  • 0.1 s
A car falls off a bridge and drops to the ground in $$0.5 s$$. Let $${g=10m/s^2}$$. How high is the bridge from the ground?
  • $$1.25 m$$
  • $$2.5 m$$
  • $$5 m$$
  • $$10 m$$
A boy running at an average speed of $$4 km/ hr$$ reaches school from his home in $$\dfrac{1}{2}\ hr$$. The distance of the school from his home is
  • $$2 km$$
  • $$8 km$$
  • $$4 km$$
  • $$6 km$$
When a bus driver travelling at a speed of 20m/s applied brakes and brings the bus to rest in 10 seconds, then retardation will be
  • $${+ 2 m/s^2}$$
  • $${+ 0.5 m/s^2}$$
  • $${-2 m/s^2}$$
  • $${-0.5 m/s^2}$$
$$A$$ and $$B$$ are arguing about uniform acceleration. $$A$$ states that acceleration means "the longer you go." $$B$$ states that acceleration means "the further you go." Who is right?
  • $$A$$
  • $$B$$
  • Both $$A$$ and $$B$$
  • None of these
A driver is driving his car along a road as shown in Figure. The driver makes sure that the speed-o-meter reads exactly 40 km/h. What happens to the velocity of the car from P to Q ? 
365669_7f18e3e453634ef4ad1fd6c0770cd405.png
  • Velocity remains constant
  • Velocity first increases then decreases
  • Velocity first decreases then increases
  • Nothing can be decided
In Fig. 2.8
365689_50bcfda872cf4fbd811780f27db26223.png
  • Retardation is uniform
  • Velocity is decreasing with time
  • Beyond M, the body has negative velocity
  • All the above statements are correct
A body cannot have a
  • zero speed and non-zero acceleration
  • non-zero speed and zero acceleration
  • constant velocity and a varying speed
  • constant speed and a varying velocity
Which of the following decreases in motion along a straight line with constant retardation? 
  • speed
  • acceleration
  • displacement
  • none of these
The slope of a distance-time graph of a moving body gives its
  • Speed
  • Displacement
  • Velocity
  • Acceleration
A van is moving on the road at $${8ms^{-1}}$$ .It accelerates at $${2ms^{-2}}$$ for a distance of 9m. How fast is it moving now?
  • $${36 ms^{-1}}$$
  • $${16 ms ^{-1}}$$
  • $${18 ms^{-1}}$$
  • $${10 ms ^{-1}}$$
A stone tied to a string is whirled in a circle. As it is revolving, the rope suddenly breaks.Then :
  • The stone flies off tangential to the circle of rotation
  • The stone moves radially inward
  • The stone moves radially outward
  • The motion of the stone depends upon its velocity
A body whose speed in a particular direction is constant :
  • must be accelerating
  • must be retarding
  • has a constant velocity in that direction
  • all the above
The displacement of a body starting from rest, and moving with an acceleration of $$1 \ { ms }^{ -2 }$$ at the end of 5 s is ____ m.
  • 12.5
  • 25
  • 7.5
  • 15
Choose the incorrect statement:
  • the speedometer of a car measures its instantaneous speed
  • the velocity of a body is always greater than the speed of that body.
  • the position-time graph of a body moving with variable velocity is a curve.
  • velocity-time graph of a uniform motion is a straight line parallel to time-axis.
A driver has to apply sudden brakes to stop his vehicle moving at $$72 \   {km}/{hr}$$ and stops within $$2 \ seconds$$. The retardation produced is then
  • $$20 \   {m}/{{s}^{2}}$$
  • $$10 \   {m}/{{s}^{2}}$$
  • $$15 \ {m}/{{s}^{2}}$$
  • $$18  \ {m}/{{s}^{2}}$$
If a trolley starts from rest with an acceleration of 2 $$m/s^2$$, the velocity of the body after 4 s would be
  • 2 m/s
  • 8 m/s
  • 4 m/s
  • 6 m/s
The SI unit for the resultant velocity is
  • m/s
  • km/s
  • cm/s
  • min/s
A body has an acceleration of $$\displaystyle -4\ { ms }^{ -2 }$$. Then its retardation is equal to:
  • $$ -4\ { ms }^{ 2 }$$
  • $$ 4\ { ms }^{ -2 }$$
  • Zero
  • Can't be determined
A driver is driving his car along a road is shown in Fig. The driver makes sure that the speedometer reads exactly 40 km/h. What happens to the velocity of the car from P to Q?
377681_de16a7717ad24b3ead7289749ada7d8c.JPG
  • Velocity remains constant
  • Velocity first increases then decreases
  • Velocity first decreases then increases
  • Nothing can be decided
A body is thrown up with an initial velocity $$u$$ and covers a maximum height of $$h$$, then $$h$$ is equal to
  • $$\displaystyle \frac{u^2}{2g}$$
  • $$\displaystyle \frac{u}{2g}$$
  • 2ug
  • none of these
Figure shows the displacement-time graphs (a) and (b) for a body moving in a straight path drawn on the same scales. Then
377693.JPG
  • slope of line in (a) is greater than the slope of line in (b)
  • slope of line in (b) is greater than the slope of line in (a)
  • slope of line in (a) is equal to the slope of line in (b)
  • nothing can be said about the slopes
Figure  shows the displacement-time graphs (a) and (b) for a body moving in a straight path drawn on the same scales. Then the velocity in case of (b) is
377695_edb2c814c0a64f3e9dd533e0a895deb8.png
  • more than the velocity in case of (a)
  • less than the velocity in case of (a)
  • equal to the velocity in case of (a)
  • square of the velocity in case of (a)
What does the speed of a body describes about its motion ?
  • Direction
  • State
  • Type
  • Rapidity
The SI unit of speed is:
  • $$m/s$$
  • $$km/s$$
  • $$cm/s$$
  • None of these
The velocity of a particle increases from u to v in a time t during which it covers a distances S. If the particle has a uniform acceleration, which one of the following equations does not apply to the motion?
  • 2 S = (v + u) t
  • $$a = \displaystyle \frac{v - u}{t}$$
  • $$v^2 = u^2 - 2 aS$$
  • $$S= \displaystyle \left[ u + \frac{1}{2} at \right] t$$
A stone projected vertically upwards reaches to the level of window $$10\ m$$ from the ground. Find the magnitude of the velocity of the stone at the time of its projection.
  • $$\displaystyle { 7\ ms }^{ -1 }$$
  • $$\displaystyle { 36\ ms }^{ -1 }$$
  • $$\displaystyle { 28\ ms }^{ -1 }$$
  • $$\displaystyle { 14\ ms }^{ -1 }$$
An automobile travelling with the speed of $$\displaystyle 72\ km {h}^{-1} $$ can be stopped within a distance of $$20\ m$$, by applying brakes. Determine the retardation.
  • $$\displaystyle -100 {ms} ^{-2} $$
  • $$\displaystyle -10 {ms} ^{-2} $$
  • $$\displaystyle 5 {ms} ^{-2} $$
  • $$\displaystyle -5 {ms} ^{-2} $$
In the above shown figure, the velocity
377706.JPG
  • increases between point O and A
  • increases between point A and B
  • decreases between points A and B
  • is zero throughout
The ratio of magnitude of velocity of projection in the upward motion to the magnitude of velocity of the body on reaching the point of projection in its downward motion is_____ .
  • 9 : 1
  • 1 : 1
  • 2 : 1
  • 4 :1
Tripling the speed of a motor car multiplies the distance needed for stopping it by
  • 3
  • 6
  • 9
  • some other number
0:0:1


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