Work, Energy And Power MCQs

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Work is something that is accomplished by the action of a force. The measure of transfer of energy occurs when an object is moved by a distance due to an external force applied in the direction of the displacement. If we apply a constant force, then the work can be calculated by multiplying the distance covered by the component and the force which is acting along the path. To express this mathematically, work done W is equal to the force exerted f times the distance covered d, or

W = fd.

The time rate at which the work is being done or energy is delivered is called power, which can be expressed as the amount of work done W, or energy transferred, against the time interval t or W/t. The Units of power can be expressed as work (or energy) per unit time, foot-pounds per minute, joules per second (or watts), and ergs per second. Power can also be expressed as the product of the force applied to move an object and the speed of the object in the direction of the force.

The capacity for doing work that exists in potential, kinetic, thermal, electrical, chemical, nuclear, or other various forms is called energy. Energy can neither be created nor be destroyed but it can be transferred from one form to the other like heat energy can be converted into light energy, chemical energy can be converted into heat energy etc.

MCQs based of Work, Energy & Power

Ques 1. The energy held by an object due to its motion is

Motion Energy
Kinetic Energy
Potential Energy
Total Energy

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Answer: (b) Kinetic Energy

Explanation: The energy an object possesses due to its motion is called Kinetic Energy. In order to accelerate an object, we must apply a force that requires us to do work. The energy is being transferred to the object after the work has been done and so the object would be moving with a new constant speed.

Ques 2. Kinetic Energy is

Scalar
Vector
Tensor
None of these

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Answer: (b) Scalar

Explanation: Kinetic energy is a scalar quantity not a vector as it does not have a direction. unlike velocity, acceleration, force. So a cricket ball thrown to the right with a velocity of 10 m/s, has the exact same kinetic energy as a cricket ball thrown down with a velocity of 10 m/s.

Ques 3. In a demonstration, a sharp-shooter fires a bullet of mass 50.0 g with speed 200 m s-1 on soft plywood of thickness 2.00 cm. The bullet comes through the wood with only 10% of its initial kinetic energy. What is the speed of the bullet when it comes out of the plywood?

61 ms-1
100 ms-1
63.2 ms-1
65.7 ms-1

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Answer: (c) 63.2 ms-1

Explanation: The initial kinetic energy of the bullet is mv2/2 = 1000 J. The Final kinetic energy of the bullet is 0.1×1000 = 100 J. If vf is the speed in which the bullet emerges,

12m vf2 = 100 J

Vf = 2 100 J0.05 kg

vf= 63.2 ms-1

Ques 4. How fast would a 1 kg bowling ball travel if it had the same kinetic energy as that of the elephant provided the mass of the elephant is 6000 kg and velocity given is 10 m/s?

1000 m/s
775 m/s
625 m/s
820 m/s

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Answer: (b) 775 m/s

Explanation: Kbowling ball = Kelephant

12 mbowling ball.v2 =12 melephant.v2

vbowling ball= mass of elephant.v2 mass of ball = 775 m/s

Ques 5. The energy possessed by a body due its position is

Kinetic Energy
Potential Energy
Total Energy
Position Energy

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Answer: (b) Potential Energy

Explanation: The energy that is possessed by a body due to its position relative to other objects is called potential energy which stresses within itself, its electric charge, or other factors.

Ques 6. Scalar Product is

A.B = AB sin x
A x B = AB sin x
A.B = AB cos x
A x B = AB cos x

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Answer: (c) A.B= AB cos x

Explanation: The scalar or dot product of two vectors A and B is written as A.B and is a scalar quantity given by : A.B = AB cos θ, where θ is the angle between A and B. It can be positive, negative or zero depending upon the value of θ.

Ques 7. Scalar Product is

Commutative
Not Commutative
Both Commutative and Non-Commutative
None of these

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Answer: (c) Commutative

Explanation: The scalar product is commutative. This means a.b = b.a

Ques 8. Scalar product obeys the distributive law which means

A.(B+C)=A.B+A.C
Ax(B+C)=AxB+AxC
Both a and b
None of these

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Answer: (a) A.(B+C)=A.B+A.C

Explanation: Scalar product obeys the distributive law:

(B + C) = A.B + A.C

Further, λ A. (λ B) = λ (A.B)

where λ is a real number.

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Ques 9. Work is expressed as:

W= F.d
W= F x d
W= FD
None of these

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Answer: (a) W=F.d

Explanation: Work can be expressed as the product of force and displacement. It is the application of force along with displacement.

Ques 10. Potential and Kinetic energy are:

Mechanical energy
Electrical energy
Magnetic energy
None of these

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Answer: (a) Mechanical Energy

Explanation: Mechanical Energy is the sum of the kinetic energy (energy of motion), and the potential energy, (energy stored in a system by reason of the position of its parts.)

Ques 11. Power is expressed as

P = dW/dt
P = F * d
P = E
P = dE/dt

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Answer: (a) P = dW/dt

Explanation: The rate of change of work is called power. Hence,

P = dW/dt.

Instantaneous power = Force x instantaneous speed.

Average power = total work / total time.

Ques 12. Energy involved in creating work _____

Gets used up
Gets transferred
Gets exhausted
Gets lost

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Answer: (b) Gets transferred

Explanation: Energy engaged with making work gets moved or changed over into another form of energy. Energy can neither be created nor be destroyed. Thus, the energy included will get changed over into another type of energy. Generally in mechanical work, the energy gets scattered as heat energy.

Ques 13. An object with weight of 100 N is kept at a height of 15m. Find the Potential Energy of the object at that height.

1500 J
1510 J
1520 J
1530 J

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Answer: Potential Energy is given by, PE=mgH

Given mg=100N and H=15 m

PE=100×15=1500 J

Ques 14. The work done by a body is 50 kJ, which it attains while reaching a height of 5 m. By what difference has the energy of the body changed?

50 kJ
-50 kJ
25 kJ
10 kJ

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Answer: (a) 50 kJ

Explanation: According to the work-energy theorem, the entire change in kinetic energy is equal to the entire work done. Therefore, the entire change in energy is 50 kJ. Since only the ‘amount’ has been asked, the sign, which denotes the direction of energy transfer, doesn't matter.

Ques 15. A cricket ball having 7 kg of mass which is moving with a velocity of 20 m/s covers a height of 8.75 m vertically. Calculate the work done in J? Assume g = 10 m/s².

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Answer: (a) 0

Explanation: According to the work-energy theorem, the total work done on a body is equal to the change in the total energy.

K.E. = 12mv²

P.E. = mgH. By using these, we can find out the net change in the kinetic and potential energies at the starting and after covering a distance of 8.75 m. Since, the total change in energy is 0, the work done is 0.

Ques 16. Work done is the scalar product of

Force and displacement vectors
Force and distance
All of these
None of these

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Answer: (a) Force and displacement vectors

Explanation: Work done is a scalar product of force and displacement, which are both vectors.

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Work, Energy And Power MCQs

MCQs based of Work, Energy & Power

CBSE CLASS XII Related Questions

1.
Draw the number of scattered particles versus the scattering angle graph for scattering of alpha particles by a thin foil. Write two important conclusions that can be drawn from this plot.

2.
Two small identical metallic balls having charges \( q \) and \( -2q \) are kept far at a separation \( r \). They are brought in contact and then separated at distance \( \frac{r}{2} \). Compared to the initial force \( F \), they will now:

3.
Two thin lenses of focal length \( f_1 \) and \( f_2 \) are placed in contact with each other coaxially. Prove that the focal length \( f \) of the combination is given by \[ f = \frac{f_1 f_2}{f_1 + f_2}. \]

4.
Photoemission of electrons occurs from a metal (\( \phi_0 = 1.96 \, \text{eV} \)) when light of frequency \( 6.4 \times 10^{14} \, \text{Hz} \) is incident on it. Calculate: Energy of a photon in the incident light, The maximum kinetic energy of the emitted electrons, and The stopping potential.

5.
What is displacement current (\( i_d \))? Considering the case of charging of a capacitor, show that \( i_d = \varepsilon_0 \frac{d\Phi_E}{dt} \). What is the value of \( i_d \) for a conductor across which a constant voltage is applied?

6.
If both the number of protons and the neutrons are conserved in each nuclear reaction, in what way is mass converted into energy (or vice versa) in a nuclear reaction? Explain.

Similar Physics Concepts

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Work, Energy And Power MCQs

MCQs based of Work, Energy & Power

CBSE CLASS XII Related Questions

1. Draw the number of scattered particles versus the scattering angle graph for scattering of alpha particles by a thin foil. Write two important conclusions that can be drawn from this plot.

2.Two small identical metallic balls having charges \( q \) and \( -2q \) are kept far at a separation \( r \). They are brought in contact and then separated at distance \( \frac{r}{2} \). Compared to the initial force \( F \), they will now:

3.Two thin lenses of focal length \( f_1 \) and \( f_2 \) are placed in contact with each other coaxially. Prove that the focal length \( f \) of the combination is given by \[ f = \frac{f_1 f_2}{f_1 + f_2}. \]

4.Photoemission of electrons occurs from a metal (\( \phi_0 = 1.96 \, \text{eV} \)) when light of frequency \( 6.4 \times 10^{14} \, \text{Hz} \) is incident on it. Calculate: Energy of a photon in the incident light, The maximum kinetic energy of the emitted electrons, and The stopping potential.

5.What is displacement current (\( i_d \))? Considering the case of charging of a capacitor, show that \( i_d = \varepsilon_0 \frac{d\Phi_E}{dt} \). What is the value of \( i_d \) for a conductor across which a constant voltage is applied?

6. If both the number of protons and the neutrons are conserved in each nuclear reaction, in what way is mass converted into energy (or vice versa) in a nuclear reaction? Explain.

Similar Physics Concepts

Comments

SUBSCRIBE TO OUR NEWS LETTER

1.
Draw the number of scattered particles versus the scattering angle graph for scattering of alpha particles by a thin foil. Write two important conclusions that can be drawn from this plot.

2.
Two small identical metallic balls having charges \( q \) and \( -2q \) are kept far at a separation \( r \). They are brought in contact and then separated at distance \( \frac{r}{2} \). Compared to the initial force \( F \), they will now:

3.
Two thin lenses of focal length \( f_1 \) and \( f_2 \) are placed in contact with each other coaxially. Prove that the focal length \( f \) of the combination is given by \[ f = \frac{f_1 f_2}{f_1 + f_2}. \]

4.
Photoemission of electrons occurs from a metal (\( \phi_0 = 1.96 \, \text{eV} \)) when light of frequency \( 6.4 \times 10^{14} \, \text{Hz} \) is incident on it. Calculate: Energy of a photon in the incident light, The maximum kinetic energy of the emitted electrons, and The stopping potential.

5.
What is displacement current (\( i_d \))? Considering the case of charging of a capacitor, show that \( i_d = \varepsilon_0 \frac{d\Phi_E}{dt} \). What is the value of \( i_d \) for a conductor across which a constant voltage is applied?

6.
If both the number of protons and the neutrons are conserved in each nuclear reaction, in what way is mass converted into energy (or vice versa) in a nuclear reaction? Explain.