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Science M.C.Q. [1 M]

Work, Power And Energy · CBSE STD 9 (CBSE - English Medium). 186 questions.

Questions · Page 1 of 4

M.C.Q. [1 M]

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MCQ 11 Mark
You have to push with $15\ N$ of force to move it $10$ meters. How much work do you do?
  • A
    $15$ Joules
  • ✓
    $150$ Joules
  • C
    $1.5$ Joules
  • D
    $67$ Joules
Answer
Correct option: B.
$150$ Joules
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MCQ 21 Mark
Potential energy increases:
  • ✓
    As the height increases
  • B
    As the mass decreases
  • C
    As the velocity increases
  • D
    None of the above
Answer
Correct option: A.
As the height increases
Potential energy of an object of mass m at height h, $P.E = mgh$
$\Rightarrow P.E \ \alpha\ h$
Therefore, potential energy increases as the height increases.
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MCQ 31 Mark
Ne megawatt is equivalent to:
  • A
    $10^2 \mathrm{~W}$
  • ✓
    $10^6 \mathrm{~W}$
  • C
    $10^4 \mathrm{~W}$
  • D
    $10^8 \mathrm{~W}$
Answer
Correct option: B.
$10^6 \mathrm{~W}$

Prefix Mega means $10^6$.
So, $1$ Megawatt = $1 \times 10^6 \mathrm{~W}$

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MCQ 41 Mark
You lift a suitcase from the floor and keep it on the table. The work done by you on the suitcase depends on:
  • A
    The path taken by the suitcase
  • B
    Your weight
  • ✓
    The weight of the suitcase
  • D
    The time taken by you in doing so
Answer
Correct option: C.
The weight of the suitcase
The work done by a person in lifting an object is stored as its potential energy mgh.
Hence, work done depends on the weight of the object mg.
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MCQ 51 Mark
Does the Law of Conservation of energy apply to machines?
  • ✓
    No, as machines require a constant input of energy in order to work
  • B
    Yes, the energy required to maintain motion is balanced by the energy lost to friction
  • C
    Yes, but only to perpetual motion machines
  • D
    No, as the law would apply to only perpetual motion machines
Answer
Correct option: A.
No, as machines require a constant input of energy in order to work
Machines require input work to be done on them, which increases the potential, or kinetic energy, or both, of the system.
However this work is done on the machines by external systems that utilize their energies to convert them to work.
So even though Law of Conservation of Energy holds for the entire system as a whole, it does not stand for the machines alone.
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MCQ 61 Mark
Identify the best definition of energy?
  • A
    Anything that has mass and takes up space
  • B
    Distance moved in a period of time
  • ✓
    Ability to do work
  • D
    Mode of opperation
Answer
Correct option: C.
Ability to do work

Energy is defined as the ability to do work and its $SI$ unit is Joule.

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MCQ 71 Mark
The device which converts mechanical energy into energy which runs our microwave oven is:
  • A
    Electric motor.
  • ✓
    Alternator.
  • C
    Turbine.
  • D
    Electric heater.
Answer
Correct option: B.
Alternator.
Alternator is the device that converts mechanical energy into energy, which runs in microwave oven.
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MCQ 81 Mark
A rocket rises up in the air due to the force generated by the fuel. The work done by the:
  • A
    Fuel is negative work and that of force of gravity is positive work.
  • ✓
    Fuel is positive work and that of force of gravity is negative work.
  • C
    Both fuel and force of gravity do positive work.
  • D
    Both fuel and force of gravity do negative work.
Answer
Correct option: B.
Fuel is positive work and that of force of gravity is negative work.
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MCQ 91 Mark
The work done on an object does not depend on the:
  • A
    Displacement.
  • B
    Angle between force and displacement.
  • C
    Force applied.
  • ✓
    Initial velocity of the object.
Answer
Correct option: D.
Initial velocity of the object.
The work done on an object does not depend upon the initial velocity of the moving object.
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MCQ 101 Mark
Work done by a body is:
  • ✓
    Negative, positive or zero
  • B
    Always positive
  • C
    Always zero
  • D
    Always negative
Answer
Correct option: A.
Negative, positive or zero
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MCQ 111 Mark
Which of the following is not an example of potential energy?
  • A
    A vibrating pendulum at its maximum displacement from the mean position
  • B
    A body at rest at some height from the ground
  • C
    A wound clock-spring
  • ✓
    A vibrating pendulum when it is just passing through the mean position
Answer
Correct option: D.
A vibrating pendulum when it is just passing through the mean position
Whenever a body is at some height from the mean $($base$)$ position or at a state of extension $($or contraction$),$ the body will have some potential energy. But when the pendulum is passing the mean position, the height from the base is $0.$ Hence a vibrating pendulum at the mean position has no potential energy.
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MCQ 121 Mark
Which mathematical relation of energy of a stone of mass $m$ falling freely from height $h$ remains conserved at every point in its downward motion?
  • A
    $\text{E}=\text{mgh}$
  • B
    $\text{E}=\frac{1}{2}\text{mv}^2$
  • ✓
    $\text{E}=\text{mgh}+\frac{1}{2}\text{mv}^2$
  • D
    None of these
Answer
Correct option: C.
$\text{E}=\text{mgh}+\frac{1}{2}\text{mv}^2$
$\text{E}=\text{mgh}+\frac{1}{2}\text{mv}^2$ mathematical relation of energy of a stone of mass $m$ falling freely from height $h$ remains conserved at every point in its downward motion.
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MCQ 131 Mark
Which one of the following possesses potential energy?
  • A
    Moving vehicle on the road
  • B
    A running athlete
  • C
    Stone on the road
  • ✓
    A stretched rubber band
Answer
Correct option: D.
A stretched rubber band
Moving vehicle on the road possesses kinetic energy.
A running athlete possesses kinetic energy.
Stone on the road possesses kinetic energy.
A stretched rubber band possesses potential energy.
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MCQ 141 Mark
How much work they do in just holding it?
  • A
    $250J$
  • B
    $2500J$
  • ✓
    $0J$
  • D
    $625J$
Answer
Correct option: C.
$0J$
The work done by a constant force of magnitude F on a point that moves a displacement (not distance) s in the direction of the force is given by:
$W = F × s$
As the men are just holding the box the value of s is $0.$
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MCQ 151 Mark
Kinetic Energy is defined as:
  • A
    Energy stored due to its location.
  • ✓
    Energy of motion.
  • C
    Energy stored in the bonds of molecules.
  • D
    Heat energy.
Answer
Correct option: B.
Energy of motion.
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MCQ 161 Mark
In the $SI$ system, the unit of potential energy is:
  • A
    Newton
  • ✓
    Joule
  • C
    Watt
  • D
    Metre per second
Answer
Correct option: B.
Joule
Joule
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MCQ 181 Mark
Kinetic energy of a body depends on its:
  • A
    Position
  • ✓
    Velocity
  • C
    Shape
  • D
    Colour
Answer
Correct option: B.
Velocity
$\text{K.E.}=\frac{1}{2}​\text{mv}^2 $
So the kinetic energy of a body depends upon its mass and velocity.
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MCQ 191 Mark
A girl is carrying a school bag of $3\ kg$ mass on her back and moves $200\ m$ on a levelled road. If the value of g be $10\ m/s^2$, the work done by the girl against the gravitational force will be:
  • A
    $6000\ J$
  • B
    $0.6\ J$
  • ✓
    $0\ J$
  • D
    $6\ J$
Answer
Correct option: C.
$0\ J$

The girl is moving with the bag on a levelled road. Her direction of motion is perpendicular to the direction of gravitational force. So, work done by the girl against gravity is zero.

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MCQ 201 Mark
The linear momentum of a body of mass $2\ kg$ is 16kgms$−1$. What is its $K. E?$
  • ✓
    $64\ J$
  • B
    $70\ J$
  • C
    $60\ J$
  • D
    None of these
Answer
Correct option: A.
$64\ J$
$64\ J$
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MCQ 211 Mark
A boy is pushing hard on a wall. Is he doing work?
  • ✓
    No
  • B
    Can't say
  • C
    May have done some work
  • D
    Yes
Answer
Correct option: A.
No

Work = Force $\times $ Displacement
Here, the wall is not moving although the boy is pushing hard.
$\therefore$ Displacement $= 0$
$\therefore$ Work $= 0$

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MCQ 221 Mark
A stone weighing $1\ kg$ is dropped from rest from a height of $4$ metres above the ground. When it has free-fallen $1$ metre its total energy with respect to the ground is:
  • A
    $15\ J$
  • ✓
    $40\ J$
  • C
    $20\ J$
  • D
    $30\ J$
Answer
Correct option: B.
$40\ J$
$40\ J$
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MCQ 231 Mark
Work done upon a body is:
  • A
    A vector quantity
  • ✓
    A scalar quantity
  • C
    Always positive
  • D
    Always negative
Answer
Correct option: B.
A scalar quantity
Work done due to displacement caused by a force is a scalar quantity, since it has only magnitude and no direction.
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MCQ 241 Mark
A body is falling a height $h$. After it has fallen a height $\frac{\text{h}}{2}$. it will possess
  • A
    Only potential energy
  • B
    Only kinetic energy
  • ✓
    Half potential energy and half kinetic energy
  • D
    More kinetic and less potential energy
Answer
Correct option: C.
Half potential energy and half kinetic energy
When the body is height $h$; its potential energy is at maximum and kinetic energy is zero. When the body hits the ground, its potential energy becomes zero and kinetic energy is at maximum. At mid$-$way i.e., half the height; its potential energy becomes half of the maximum potential energy and same happens to the kinetic energy.
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MCQ 251 Mark
Potential energy and kinetic energy are types of:
  • A
    Electrical energy
  • B
    Magnetic energy
  • C
    Thermal energy
  • ✓
    Mechanical energy
Answer
Correct option: D.
Mechanical energy
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MCQ 261 Mark
A fruit hanging from the top branch of a tree possesses:
  • ✓
    Gravitational potential energy
  • B
    Elastic potential energy
  • C
    Kinetic energy
  • D
    Sound energy
Answer
Correct option: A.
Gravitational potential energy
A fruit, hanging from the top branch of a tree, is at rest at a certain height from the earth"s surface.
So, it possesses gravitational potential energy.
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MCQ 271 Mark
According to the law of conservation of energy, total energy is:
  • A
    Increasing
  • B
    Decreasing
  • ✓
    Constant
  • D
    None of these
Answer
Correct option: C.
Constant
The law of conservation of energy states that the total energy is constant in any process. Energy may change in form or be transferred from one system to another, but the total remains the same.
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MCQ 281 Mark
Heat Energy is called:
  • A
    Radiant Energy
  • B
    Chemical Energy
  • ✓
    Thermal Energy
  • D
    Mechanical Energy
Answer
Correct option: C.
Thermal Energy
c. Thermal Energy
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MCQ 291 Mark
Which one of the following is not the unit of energy?
  • A
    Joule
  • B
    Newton metre
  • ✓
    Kilowatt
  • D
    Kilowatt hour
Answer
Correct option: C.
Kilowatt
We know that, joule, newton metre and kilowatt hour are the units of energy and the kilowatt is the unit of power.
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MCQ 301 Mark
A ball rolling on the ground possesses:
  • ✓
    Kinetic energy
  • B
    Potential energy
  • C
    No energy
  • D
    Heat energy
Answer
Correct option: A.
Kinetic energy
A moving car possesses mechanical energy due to its motion $($kinetic energy$)$. A moving baseball possesses mechanical energy due to both its high speed $($kinetic energy$)$ and its vertical position above the ground $($gravitational potential energy$)$.
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MCQ 311 Mark
A car is accelerated on a levelled road and acquires a velocity $4$ times of its initial velocity. During this process, the potential energy of the car:
  • ✓
    Does not change.
  • B
    Becomes twice that of initial potential energy.
  • C
    Becomes $4$ times that of initial potential energy.
  • D
    Becomes $16$ times that of initial potential energy.
Answer
Correct option: A.
Does not change.

Potential energy of an object depends only on its position above the ground and mass. So, the potential energy of a car traveling on a leveled road does not change.

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MCQ 321 Mark
A wristwatch works on the basis of energy possessed by:
  • A
    A pendulum.
  • B
    A spring.
  • C
    A battery only.
  • ✓
    Can be $(b)$ or $(c).$
Answer
Correct option: D.
Can be $(b)$ or $(c).$
A battery sends an electric current to a tiny, tuning-fork-shaped piece of quartz, causing it to oscillate at $32,768$ vibrations per second. (This is why mechanical watches, whose springs steadily release tension, have smoother second-hand movement than quartz watches).
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MCQ 331 Mark
Which of the following is an example of an object with Kinetic energy?
  • ✓
    Boy running on field
  • B
    Bent bow
  • C
    Stone at a height
  • D
    Water stored in a reservoir
Answer
Correct option: A.
Boy running on field

kinetic energy is energy possessed by body due to virtue of its motion.
only boy in option $A$ is in motion so only he has some kinetic energy.
rest option have things at rest so no kinetic energy.

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MCQ 341 Mark
What are the two types of Mechanical Energy$? (ME)$
  • ✓
    Kinetic and Potential Energy.
  • B
    Kinetic and Nuclear Energy.
  • C
    Potential and Chemical Energy.
  • D
    Thermal and Kinetic Energy.
Answer
Correct option: A.
Kinetic and Potential Energy.
Kinetic and Potential Energy.
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MCQ 351 Mark
A man carries a heavy box on his head on a horizontal plane from one place to another. In this case, he does:
  • A
    Maximum work
  • ✓
    No work
  • C
    Negative work
  • D
    Minimum work
Answer
Correct option: B.
No work
A man carrying a box on his head:
In this case, the force acting on the man is the weight of the box, which is acting downwards.
The displacement of the man is along the horizontal direction.
Therefore, the force and the displacement are perpendicular to each other. So there is no work involved in this process.
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MCQ 361 Mark
A girl weighing $400N$ climbs a vertical ladder. If the value of g be $10\ ms^2$, the work done by her after climbing $2m$ will be:
  • A
    $200J$
  • ✓
    $800J$
  • C
    $8000J$
  • D
    $2000J$
Answer
Correct option: B.
$800J$

Weight of the girl $(W) = 400N$
Vertical height $(h) = 2m$
Acceleration due to gravity $(g) = 10m/s^2$
We can calculate the work done against gravity in moving a body of mass $(m)$ by a height $(h)$ as,
Work done in lifting a body $= ($Weight of body$)($Vertical distance$)$
So,
$W = (m)(g)(h)$
So,
Work done in lifting a body
$= (400)(2)J$
$= 800J$

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MCQ 371 Mark
Two masses $m$ and $2m$ are dropped from certain height $‘h’.$ Then on reaching the ground:
  • A
    $K.E.$ of them will be equal.
  • B
    $K.E.$ of the heavier is $4$ times the $K.E.$ of the lighter.
  • C
    $K.E.$ of the lighter is $4$ times the $K.E.$ of the heavier.
  • ✓
    $K.E.$ of the heavier is more than that of the lighter.
Answer
Correct option: D.
$K.E.$ of the heavier is more than that of the lighter.
$K.E.$ of the heavier is more than that of the lighter.
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MCQ 381 Mark
Unit used in selling electrical energy to consumer is:
  • A
    Volt−Ampere
  • ✓
    Kilowatt−hour
  • C
    Volt/second
  • D
    None of these
Answer
Correct option: B.
Kilowatt−hour

 The commercial unit of electrical energy is Kilowatt $−$ hour (kWh).
$1\ kWh$ is equal to $1$ unit of energy.

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MCQ 391 Mark
You drop a $5\ kg$ ball from a height of $2\ m.$ Just before it reaches the ground, what type of energy does it have$?$
  • A
    Potential Energy
  • ✓
    Kinetic Energy
  • C
    Nuclear Energy
  • D
    Chemical Energy
Answer
Correct option: B.
Kinetic Energy
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MCQ 401 Mark
The law of conservation of energy implies that the:
  • A
    Total mechanical energy is conserved
  • B
    Total kinetic energy is conserved
  • C
    Total potential energy is conserved
  • ✓
    Sum of all kinds of energies is conserved
Answer
Correct option: D.
Sum of all kinds of energies is conserved
Law of conservation of energy implies that energy can neither be created nor destroyed, but can merely be transfered from one form to other. These forms are varied. Thus, when considering all forms of energy,$($including workdone$)$ the total sum never changes.
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MCQ 411 Mark
What is potential energy?
  • ✓
    Energy of an object due to its position or arrangement in a system
  • B
    Energy of an object due to its nature or arrangement in a system
  • C
    Energy of an object due to its shape or arrangement in a system
  • D
    None
Answer
Correct option: A.
Energy of an object due to its position or arrangement in a system
The potential energy is the stored energy of an object due to its position.
some examples of potential energies are gravitational potential energy, Electrostatic potential energy and elastic energy etc.
A body placed at ground will have less gravitational potential energy than a body placed at some height. therefore, potential energy changes by changing the position of object.
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MCQ 421 Mark
All types of energy that exist in the nature can be categorized as either kinetic or potential. Choose correct statement regarding the validity of above sentence:
  • A
    This statement is true for thermal and and mechanical, but not elastic
  • B
    This statement is true for all different types of energy
  • ✓
    This statement is false, except in the case of mechanical energy
  • D
    This statement is never true
Answer
Correct option: C.
This statement is false, except in the case of mechanical energy
There exists other types of energies such as light energy, sound energy, nuclear energy etc. which are neither kinetic nor potential.
Energies in the form of mechanical energy are categorized as either kinetic or potential energy.
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MCQ 431 Mark
A stone rubbed on a rough floor and placed on the skin will show heating sensation, because:
  • ✓
    Friction causes heat.
  • B
    Heat flows from the skin to stone.
  • C
    Heat flows from stone to the skin.
  • D
    Heat cannot flow.
Answer
Correct option: A.
Friction causes heat.
When a fire stone is rubbed on a hard and rough surface we get fire. This is due to friction.
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MCQ 441 Mark
When heated, molecules absorb $......$ and their capacity to do $......$ increases:
  • A
    Work ,energy
  • ✓
    Energy ,work
  • C
    Heat, work
  • D
    Energy ,heat
Answer
Correct option: B.
Energy ,work
When heated, molecules absorb the energy, and their capacity to do work increases.
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MCQ 451 Mark
Work done by the gravitational force of earth on a satellite along a circular path is:
  • ✓
    $O$
  • B
    Minimum
  • C
    Max
  • D
    All of these
Answer
Correct option: A.
$O$
$O$
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MCQ 461 Mark
On listening to his friend, Amit said “Moon does not work as it goes round our earth”, because:
A: Moon displaces perpendicular to direction of force.
B: No force acts on the moon.
C: Momentum change is non-zero.
Which of the combination is/ are correct$?$
  • ✓
    $A $ and $C$ only.
  • B
    $A$ and $B$ only.
  • C
    $A, B$ and $C.$
  • D
    $B$ and $C$ only.
Answer
Correct option: A.
$A $ and $C$ only.

 As the moon orbits the Earth, the force of gravity acting upon the moon provides the centripetal force required for circular motion.
This would mean that the force is always directed perpendicular to the direction that the object is being displaced.

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MCQ 471 Mark
Which of the following physical quantities is different from others$?$
  • A
    Work
  • B
    Kinetic energy
  • ✓
    Force
  • D
    Potential energy
Answer
Correct option: C.
Force

 Kinetic energy is the energy possessed by the body by virtue of its motion and potential energy is the energy possessed by the virtue of its position and shape. Energy is required to do work.
Hence work, kinetic energy, potential energy all can be measured using same unit, i.e joule.
So, force is the physical quantity here which is different from others as given by product of mass and acceleration. $S.I$ unit of force is $N ($newton$).$

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MCQ 481 Mark
When a body falls freely towards the earth, then its total energy:
  • A
    Decreases
  • B
    Increases
  • C
    First increases and then decreases
  • ✓
    Remains constant
Answer
Correct option: D.
Remains constant
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MCQ 491 Mark
Find the correct statement:
  • A
    $1$ Gigawatt is equal to $10^9W$
  • B
    Power is the rate of doing work
  • ✓
    Both $a$ and $b$
  • D
    None of these
Answer
Correct option: C.
Both $a$ and $b$
Both $a$ and $b$
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MCQ 501 Mark
The commercial unit of energy is:
  • A
    Watt.
  • B
    Watt$-$hour.
  • ✓
    Kilowatt$-$hour.
  • D
    Kilowatt.
Answer
Correct option: C.
Kilowatt$-$hour.
Kilowatt$-$hour is the commercial unit of electricity.
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