MCQ Questions for Class 9 Physics Work And Energy Quiz 8

An electric heater has a rating of 2 kW, 220 V. The cost of running the heater for 10 hours at the rate of Rs 350 per unit is Rs ____

0%
216
0%
165
0%
209
0%
105

Explanation

Power is energy consumed per unit time.

Here, energy consumed

$=P=2kW=2000W$ and time

$=t=10hr=36000s$

$P=\dfrac{E}{t}$

$\implies E=Pt=2kW\times 10h=20kWh=20units$

Since

$1unit=1kWh$

Cost

$=20\times 350=Rs 7000$

What is the work done by gravity on a load of

$50 \ kg$ carried by porter while walking along the platform?

0%
$0 J$
0%
$10 J$
0%
$50 J$
0%
$500 J$

The energy directly related to the speed of a moving body and its mass is:

0%
kinetic
0%
potential
0%
solar
0%
electric

A heavy object has ....... gravitational potential energy than a lighter one.

0%
less
0%
more
0%
same
0%
none of these

Explanation

Gravitational potential energy is given by

$PE=mgh$

where

$m$ is mass so heavy object means more mass and more mass means more potential energy.

The electricity tariff in a town is

$Rs.3.00$ per unit. Calculate the cost of running an

$80 W$ fan for

$10 h$ a day for the month of June.

0%
$Rs. 12.00.$
0%
$Rs. 52.00.$
0%
$Rs. 72.00.$
0%
$Rs. 92.00.$

Explanation

Total time for which the fan is used

$= (10 hours) \times (30 days) = 300$ hours.
Energy consumed

$= (80 W) \times (300$ hours

$)$

$= 24,000 Wh = 24 kWh.$
But

$1 kWh =1$ unit.
Therefore,

$24 kWh = 24$ units
The cost of this power

$= 24$ units

$\times Rs. 3= Rs. 72.00.$

Which one of the following types of energy is possessed by a body when placed at a certain height?

0%
Kinetic energy
0%
Potential energy
0%
Heat energy
0%
Sound energy
0%
None of these

Explanation

When a body is placed at a certain height, the body possesses potential energy.

$P.E. = mgH$

$m$ ; the mass of the object

$g$ ; acceleration due to gravity

$H$ ; height gained by object

Calculate the work done when a 2N force moves a body through a distance of 10 m.

0%
10 J
0%
2 J
0%
5 J
0%
20 J

Explanation

Work done = Force applied x Distance moved

$W=F \times s$

$W = 2 \times 10 = 20\ J$

------ is done when you push a box.

0%
Displacement
0%
Motion
0%
Work
0%
Speed

Explanation

When we push a box, a force is applied. Since the box is moving, some work is done on the box. (As

$Work=(force)\times (displacement)$

Potential energy increases :

0%
As the height increases
0%
As the mass decreases
0%
As the velocity increases
0%
None of the above

Explanation

Potential energy of an object of mass

$m$ at height

$h$ ,

$P.E = mgh$

$\implies P.E \propto h$

Therefore, potential energy increases as the height increases.

Find the potential energy if a body is placed at a certain height of 5 m from the earth.

0%
196 J
0%
200 J
0%
150 J
0%
300 J
0%
None of these

The water stored in a reservoir possesses :

0%
Kinetic energy
0%
Muscular energy
0%
Potential energy
0%
Magnetic energy

Two masses

$10 \ gm$ and

$40 \ gm$ are moving with kinetic energies in the ratio

$9:25$ . The ratio of their linear momentum is:

0%
$5:6$
0%
$3:10$
0%
$6:5$
0%
$10:3$

When an aeroplane takes off from the ground :

0%
Kinetic energy increases and Potential energy decreases
0%
Potential energy increases and Kinetic energy remains constant
0%
Both Kinetic energy and Potential energy remain constant
0%
Both Kinetic energy and Potential energy increase

Explanation

Kinetic energy is due to the motion of the object and potential energy is due to relative elevation.

So as the plane takes off height increases and also its speed increase, so both kinetic and potential energy increases.

$\text{Kinetic energy} = \dfrac{1}{2}mv^2$

$\text{Potential energy} = mgH$

Which of the following is an example of an object with Kinetic energy?

0%
Boy running on field
0%
Bent bow
0%
Stone at a height
0%
Water stored in a reservoir

While running you possess certain kind of energy due to motion .What kind of energy do you possess?

0%
Potential energy
0%
Kinetic energy
0%
Electrical energy
0%
Chemical energy
0%
None of these

Kinetic energy of a body depends on its:

0%
Position
0%
Velocity
0%
Shape
0%
Colour

Explanation

$K.E.=\dfrac{1}{2} mv^2$

So the kinetic energy of a body depends upon its mass and velocity.

A force, applied on a body, is said to have done some work

0%
If the body suffers no displacement
0%
If the body suffers a displacement
0%
If the shape of the body changes
0%
If the size of the body changes

Explanation

A force, applied on a body, is said to have done some work if the body suffers a displacement. This is according to the definition of work.

$\text{work = Force} \times \text{displacement}$

.............. is said to be done only when the force applied on a body makes the body to move.

0%
Work
0%
Momentum
0%
Retardation
0%
None of these

A body is moved in a direction opposite to the direction of force acting on it. So:

0%
work is done by the force
0%
work is done against the force
0%
no work is done
0%
an infinite amount of work is done

The CGS unit of energy is :

0%
Dyne
0%
Erg
0%
Centimetre
0%
Pascal

Explanation

CGS unit of energy is

$Dyne-cm$ which is also known as

$erg$ .

Which of the following does not have potential energy ?

0%
An inflated balloon
0%
Water in a flowing river
0%
A fruit on the tree
0%
A spinning top

From the following statements find the one that is NOT correct :

0%
A flying bird has both potential and kinetic energy
0%
A ball rolling on the ground has kinetic energy but no mechanical energy
0%
A stretched rubber band has potential energy.
0%
Chemical energy can be converted into electrical energy

In which of the following cases, is a work being done?

0%
A boy pushing a wall
0%
A coolie walking with a load of 10 kg on his head
0%
A girl is climbing up the staircase
0%
A student is holding a book in hand

A boy of mass

$40\ kg$ runs up a flight of

$50$ steps, each

$10\ cm$ high in

$14\ s$ . So, work done by the boy is:

0%
$1960\ J$
0%
$19.6\ J$
0%
$980\ J$
0%
$9.8\ J$

Explanation

Mass of the boy,

$m = 40\ kg$

Number of steps =

$50$

Height of each step =

$10\ cm$

Force on the boy due to gravity,

$F=mg=40\times{9.8}N=392\ N$
While climbing up the steps, the boy does work against gravity.
Displacement in the vertical direction,

$s=(50\times{10})\ cm=500\ cm=5\ m$

Displacement is in the direction of force applied by the boy against gravity.
So, work done,

$W=F\times{s}=392\times{5}\ J=1960\ J$

A moving cricket ball possesses

0%
Kinetic energy
0%
Potential energy
0%
Chemical energy
0%
Sound energy

Explanation

A moving cricket ball possesses kinetic energy.

Formula of kinetic energy

$(KE)$ -

$KE = \dfrac{ 1 }{ 2 }mv^2$

$m$ ; mass of the ball

$v$ ; speed of the ball

Work in terms of power and time

0%
$\text{power} \times \text{time}$
0%
$\dfrac{\text{power}}{\text{time}}$
0%
$\text{power}+\text{time}$
0%
None of these

Explanation

The power is-

$Power = \dfrac{Work}{time}$

$\Rightarrow work = power \times time$

Work done by a fielder in catching a ball is

0%
Zero
0%
Positive
0%
Negative
0%
None of these

The amount of work done (or, energy spent) by a source of power

$1kW$ in

$1h$ time is:

0%
$1J$
0%
$1Wh$
0%
$1kWh$
0%
$1calorie$

Explanation

$Energy$

$spent$ =

$Power \times time$

$E=1kWh \times 1h$ =

$1kWh$

$1kWh$ is the amount of work done (or, energy spent) by a source of

$1kW$ power in

$1h$ time.

The S.I. unit of energy is

0%
erg
0%
calorie
0%
Joule
0%
None of these

Explanation

Energy is capacity of doing work. The unit of energy is same as that of work. So, S.I. unit of energy is

$joule(J)$ .

A fruit hanging from the top branch of a tree possesses

0%
gravitational potential energy
0%
elastic potential energy
0%
kinetic energy
0%
sound energy

CBSE Questions for Class 9 Physics Work And Energy Quiz 8 - MCQExams.com

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Practice Class 9 Physics Quiz Questions and Answers

CBSE Questions for Class 9 Physics Work And Energy Quiz 8 - MCQExams.com

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Practice Class 9 Physics Quiz Questions and Answers

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