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Science M.C.Q. [1 M]

Motion · CBSE STD 9 (CBSE - English Medium). 26 questions.

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M.C.Q. [1 M]

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26 questions · timed · auto-graded

MCQ 11 Mark
Which of the following could not be a unit of acceleration?
  • A
    $\mathrm{km} / \mathrm{s}^2$
  • B
    $\mathrm{cms}^{-2}$
  • ✓
    $\mathrm{km} / \mathrm{s}$
  • D
    $\mathrm{m} / \mathrm{s}^2$
Answer
Correct option: C.
$\mathrm{km} / \mathrm{s}$
Acceleration is defined as the rate of change of velocity.
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MCQ 21 Mark
Four cars $A, B, C$ and $D$ are moving on a levelled, straight road. Their distance-time graphs are shown in the given figure. Which of the following is the correct statement regarding the motion of these cars$?$
  • A
    Car $A$ is faster than car $D.$
  • ✓
    Car $B$ is the slowest.
  • C
    Car $D$ is faster than the car $C.$
  • D
    Car $C$ is the slowest.
Answer
Correct option: B.
Car $B$ is the slowest.
The slope of distance time graph gives the speed or the measure of rate of change of distance per unit time.
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MCQ 31 Mark
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.
  • ✓
    The car travels equal distances in unequal time intervals.
Answer
Correct option: D.
The car travels equal distances in unequal time intervals.
When a car runs on a circular track, its velocity changes continuously, as its direction keeps changing.
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MCQ 41 Mark
The slope of a speed-time graph gives:
  • A
    Distance travelled.
  • B
    Velocity.
  • ✓
    Acceleration.
  • D
    Displacement.
Answer
Correct option: C.
Acceleration.
The rate of change of speed per unit time is termed as acceleration.
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MCQ 51 Mark
$50.$ Which of the following can sometimes be 'zero' for a moving body$?$
  1. Average velocity.
  2. Distance travelled.
  3. Average speed.
  4. Displacement.
  • A
    only $(i)$
     
  • B
    $(i)$ and $(ii)$
  • ✓
    $(i)$ and $(iv)$
     
  • D
    only $(iv)$
Answer
Correct option: C.
$(i)$ and $(iv)$
 
Distance is the length of the actual path covered by a moving body. This implies that the distance travelled by a moving body and also its average speed can never be zero at any point of time. However, it is possible for the displacement as well as average velocity for the body to be zero at an instance during the motion of the particle.
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MCQ 61 Mark
A student draws a distance-time graph for a moving scooter and finds that a section of the graph is a horizontal line parallel to the time axis. Which of the following conclusion is correct about this section of the graph?
  • A
    The scooter has uniform speed in this section.
  • B
    The distance travelled by scooter is the maximum in this section.
  • C
    The distance travelled by the scooter is the minimum in this section.
  • ✓
    The distance travelled by the scooter is zero in this section.
Answer
Correct option: D.
The distance travelled by the scooter is zero in this section.
If distance time graph is parallel to the time axis then the object has not travelled any distance.
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MCQ 71 Mark
Which of the following could not be a unit of speed$?$
  • A
    $km/h$
  • ✓
    $s/m$
  • C
    $m/s$
  • D
    $\mathrm{mm} \mathrm{~s}^{-1}$
Answer
Correct option: B.
$s/m$

Speed is the distance travelled by a moving body per unit time.

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MCQ 81 Mark
A boy is sitting on a merry$-$go$-$round which is moving with a constant speed of $10\ \mathrm{ms}^{-1}$. This means that the boy is:
  • A
    At rest.
  • B
    Moving with no acceleration.
  • ✓
    In accelerated motion.
  • D
    Moving with uniform velocity.
Answer
Correct option: C.
In accelerated motion.
Acceleration is the rate of change of velocity, and the velocity of the merry$-$go$-$round is changing with respect to time. Thus, it will move in an accelerated motion.
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MCQ 91 Mark
he 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 $1$
  • ✓
    Equal to $1$ or less than $1$
Answer
Correct option: D.
Equal to $1$ or less than $1$
Displacement is always smaller than or equal to displacement.
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MCQ 101 Mark
A fielder pulls his hands backwards after catching the cricket ball. This enables the fielder to:
  • A
    Exert larger force on the ball.
  • ✓
    Reduce the force exerted by the ball.
  • C
    Increase the rate of change of momentum.
  • D
    Keep the ball in hands firmly.
Answer
Correct option: B.
Reduce the force exerted by the ball.
He does this to increase the change in momentum time of the ball. This helps him to save himself from getting hurt by the ball.
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MCQ 111 Mark
Which one of the following is most likely not a case of uniform circular motion?
  • A
    Motion of the earth around the sun.
  • B
    Motion of a toy train on a circular.
  • ✓
    Motion of a racing car on a circular tracki.
  • D
    Motion of hours' hand on the dial.
Answer
Correct option: C.
Motion of a racing car on a circular tracki.
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MCQ 121 Mark
 A bus moving along a straight line at $20 \mathrm{~m} / \mathrm{s}$ undergoes an acceleration of $4 \mathrm{~m} / \mathrm{s}^2$. After $2$ seconds, its speed will be:
  • A
    $8\ m/s$
  • B
    $12\ m/s$
  • C
    $16\ m/s$
  • ✓
    $28\ m/s$
Answer
Correct option: D.
$28\ m/s$

Acceleration of the moving object is $4 \mathrm{~m} / \mathrm{s}^2$
Initial velocity is $20 \mathrm{~m} / \mathrm{s}$.
Time taken is $2 \sec .$
By applying $1^{\text {st }}$ equation of motion we get,
$v=u+a t$
$=20+2(4)$
$=28 \mathrm{~m} / \mathrm{s}$

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MCQ 131 Mark
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.
  • ✓
    Velocity of a moving body is its speed in a given direction.
Answer
Correct option: D.
Velocity of a moving body is its speed in a given direction.
Velocity is a vector quantity having a magnitude and a specific direction. So, velocity is nothing but speed in a particular direction.
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MCQ 141 Mark
A car of mass $1000\ kg$ is moving with a velocity of $10 \mathrm{~ms}^{-1}$. If the velocity-time graph for this car is a horizontal line parallel to the time axis, then the velocity of car at the end of $25\ s$ will be:
  • A
    $25 \mathrm{~ms}^{-1}$
  • B
    $40 \mathrm{~ms}^{-1}$
  • ✓
    $10 \mathrm{~ms}^{-1}$
  • D
    $250 \mathrm{~ms}^{-1}$
Answer
Correct option: C.
$10 \mathrm{~ms}^{-1}$

It is given that the velocity time curve is parallel to $x$ axis hence velocity is constant with time and acceleration is $0$.

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MCQ 151 Mark
If the displacement of an object is proportional to the square of time, then the object is moving with:
  • A
    Uniform velocity.
  • ✓
    Uniform acceleration.
  • C
    Increasing acceleration.
  • D
    Decreasing acceleration.
Answer
Correct option: B.
Uniform acceleration.

We are given with the relationship that,
$x=k t^2$
Differentiating it twice we get,
$\mathrm{v}=2 \mathrm{kt}$
$\mathrm{a}=2 \mathrm{k}$
Where,
$\mathrm{v} \text { - velocity }$
$a -$ acceleration

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MCQ 161 Mark
A bus increases its speed from $36 \mathrm{~km} / \mathrm{h}$ to $72 \mathrm{~km} / \mathrm{h}$ in 10 seconds. Its acceleration is:
  • A
    $5 \mathrm{~m} / \mathrm{s}^2$
  • B
    $2 \mathrm{~m} / \mathrm{s}^2$
  • C
    $6 \mathrm{~m} / \mathrm{s}^2$
  • ✓
    $1 \mathrm{~m} / \mathrm{s}^2$
Answer
Correct option: D.
$1 \mathrm{~m} / \mathrm{s}^2$

Final velocity $=72 \mathrm{~km} / \mathrm{h}=20 \mathrm{~m} / \mathrm{s}$
Initial velocity is $36 \mathrm{~km} / \mathrm{h}=10 \mathrm{~m} / \mathrm{s}$
Time taken is $10 \sec $. So,
Acceleration $=\frac{20-10}{10}$
$=1\text{m/s}^2$

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MCQ 171 Mark
One of the following is not a vector quantity. This one is:
  • A
    Displacement.
  • ✓
    Speed.
  • C
    Acceleration.
  • D
    Velocity.
Answer
Correct option: B.
Speed.
Vector quantities have magnitude as well as direction, and they obey the laws of vector addition.
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MCQ 181 Mark
A particle is moving in a circular path of radius $r.$ The displacement after half a circle would be:
  • A
    $0$
  • B
    $\pi\text{r}$
  • ✓
    $2\text{r}$
  • D
    $2\pi\text{r}$
Answer
Correct option: C.
$2\text{r}$
Displacement is the difference between the final and initial position of a body. It is a vector quantity and is independent of the path taken. So, for the movement of half of a circle, the displacement is $2r,$ where r is the radius of the circular path.
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MCQ 191 Mark
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
    $1.08\ km/h$
  • ✓
    $0.216\ km/h$
  • D
    $0.0216\ km/h$
Answer
Correct option: C.
$0.216\ km/h$
We can convert $0.06\ m/s$ as:
$=\frac{0.06(3600)}{1000}\text{km/hr}$
$=0.216\text{km/hr}$
So, the answer is $0.216\ km/hr.$
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MCQ 201 Mark
A sprinter is running along the circumference of a big sports stadium with constant speed Which of following do you think is changing in this case?
  • A
    Magnitude of acceleration being produced.
  • B
    Distance covered by the sprinter per second.
  • ✓
    Direction in which the sprinter is running.
  • D
    Entripetal force acting on the sprit.
Answer
Correct option: C.
Direction in which the sprinter is running.
The sprinter is having a uniform circular motion in which the direction of motion continuously changes.
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MCQ 211 Mark
When a car driver travelling at a speed of $10 \mathrm{~m} / \mathrm{s}$ applies brakes and brings the car to rest in $20\ s ,$ then retardation will be:
  • A
    $+2 \mathrm{~m} / \mathrm{s}^2$
  • B
    $-2 \mathrm{~m} / \mathrm{s}^2$
  • C
    $-0.5 \mathrm{~m} / \mathrm{s}^2$
  • ✓
    $+0.5 \mathrm{~m} / \mathrm{s}^2$
Answer
Correct option: D.
$+0.5 \mathrm{~m} / \mathrm{s}^2$
The term "retardation" means negative acceleration.
Initial velocity $=10 \mathrm{~m} / \mathrm{s}$
Final velocity $=0 \mathrm{~m} / \mathrm{s}$
Time taken $=20$ s
Acceleration $=\frac{0-10}{20}$
$\Rightarrow$ Acceleration $=-0.5 \mathrm{~m} / \mathrm{s}^2$
$\Rightarrow$ Retardation $=0.5 \mathrm{~m} / \mathrm{s}^2$
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MCQ 221 Mark
A freely falling object travels $4.9m$ in $1st$ second, $14.7m$ in 2nd second, $24.5m$ in $3rd$ second, and so on. This data shows that the motion of a freely falling object is a case of:
  • A
    Uniform motion.
  • ✓
    Uniform acceleration.
  • C
    No acceleration.
  • D
    Uniform velocity.
Answer
Correct option: B.
Uniform acceleration.
The displacement of the body in equal interval of time is unequal, but acceleration is constant. The acceleration will thus be uniform.
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MCQ 231 Mark
In the speed-time graph for a moving object shown here, the part which indicates uniform deceleration of the object is:
  • A
    $ST$
  • B
    $QR$
  • ✓
    $RS$
  • D
    $PQ$
Answer
Correct option: C.
$RS$
For a speed time graph to show uniform deceleration, the slope should be negative and constant for that time interval.
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MCQ 241 Mark
The area under a speed-time graph represents a physical quantity which has the unit of:
  • ✓
    $m$
  • B
    $\mathrm{m}^2$
  • C
    $\mathrm{ms}^{-1}$
  • D
    $\mathrm{ms}^{-2}$
Answer
Correct option: A.
$m$

The area under the speed time graph gives us the distance.

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MCQ 251 Mark
A motorcycle is being driven at a speed of $20\ m/s$ when brakes are applied to bring it to rest five seconds. The deceleration produced in this case will be:
  • ✓
    $+4 \mathrm{~m} / \mathrm{s}^2$
  • B
    $-4 \mathrm{~m} / \mathrm{s}^2$
  • C
    $+0.25 \mathrm{~m} / \mathrm{s}^2$
  • D
    $-0.25 \mathrm{~m} / \mathrm{s}^2$
Answer
Correct option: A.
$+4 \mathrm{~m} / \mathrm{s}^2$

We have,
Initial velocity $= 20\ m/s$
Final velocity $= 0\ m/s$
Time taken $= 5 \sec.$
So,
Deceleration $=$ -Acceleration
$= \frac{-(0 - 20)}{5}$
$= 4\text{m/s}^2$

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MCQ 261 Mark
In which of the following cases of motion, the distance moved and the magnitude of displacement are equal?
  • ✓
    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.
Answer
Correct option: A.
If the car is moving on straight road.
The magnitude of displacement is equal to the distance travelled by a body when it travels in a straight line.
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