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This mock test of Test: Acceleration for Class 9 helps you for every Class 9 entrance exam.
This contains 10 Multiple Choice Questions for Class 9 Test: Acceleration (mcq) to study with solutions a complete question bank.
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QUESTION: 1

A bus decelerating with 4m/s^{2} changes its speed from 60 m s^{-1} to a certain value in 5 s. The final speed is:

Solution:

Acceleration = – 4m/s^{2}; Initial speed, u = 60 m s^{-1}

Time taken = 5s

Acceleration = change in velocity per unit time

a=v-u/t

v= u + at

v = 60 – 4 x 5 = 40 m/s

QUESTION: 2

If the upward direction is taken as positive what is the sign of velocity and acceleration when a body falls freely from a height.

Solution:
Both velocity and acceleration are in the downward direction. Thus, they will be considered negative as they are vectors and the upward direction is positive.

QUESTION: 3

A body moving along a straight line at 20m/s undergoes an acceleration of -4m/s^{2}. After two seconds its speed will be

Solution:

U=20m/s

a=-4m/s^{2}

t=2s

v=?

v=u+at

v=20+(-4)(2)

v=20-8

v=12m/s

QUESTION: 4

A boy throws a ball up and catches it when the ball falls back. In which part of the motion the ball is accelerating?

Solution:
When the ball moves upward ,the force of gravitation is acting in the opposite direction of the ball that is why in that case acceleration is negative or in other words deceleration takes place, but when the ball is moving downwards the force of gravitation is in the same direction of the motion of the ball thus acceleration takes place in this case .so option A is the correct answer.

QUESTION: 5

Choose the correct option:

Solution:

Distance is a **scalar quantity** that refers to "how much ground an object has covered" during it's motion.

Acceleration is a **vector quantity** that is defined as the rate at which an object changes it's velocity.

Velocity is a **vector quantity** which refers to the speed of an object in a particular direction.

QUESTION: 6

The ratio of C.G.S. to M.K.S. unit of acceleration is:

Solution:

M.K.S. unit of acceleration = 1m/s^{2}

C.G.S unit of acceleration/ M,K.S unit of acceleration =

1cm/s^{2} / 1m/s^{2}

= 1cm / 100 cm

= 1/100

=1:100

QUESTION: 7

The S.I. unit of acceleration is:

Solution:

Calculating acceleration involves dividing velocity by time Or we can say, dividing the meter per second by the second. i.e.

[ m/s^{2} = m/s / s ]

Therefore, option ( c) ms^{-2} is the correct answer.

QUESTION: 8

If a moving body comes to rest, then its acceleration is-

Solution:

If a moving body comes to rest, then its acceleration is negative, as it's velocity becomes zero.

QUESTION: 9

If the velocity of a body changes uniformly from u to v in time t, the sum of average velocity and acceleration is:

Solution:

**The correct option is Option D **

Average velocity = (u+v)/t

Acceleration = (v-u)/t

Thus sum of average velocity and acceleration

= (u + v )/t + (v-u)/t

= 2v/t

QUESTION: 10

Acceleration is defined as the rate of change of:

Solution:
Acceleration is a vector quantity that is defined as the rate at which an object changes its velocity. An object is accelerating if it is changing its velocity.

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