Power

Power MDCAT MCQs with answers

30 past paper MCQs on Power, from the Work and Energy unit of MDCAT Physics. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.

Read the notes first Practise the unit as a quiz

1.The kilowatt-hour is a unit of: (MDCAT 2020)

  1. electric energy
  2. power
  3. momentum
  4. intensity
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Correct answer: (a) electric energy

It is a power multiplied by a time, so it measures energy.

2.One kilowatt-hour is equal to: (MDCAT 2020)

  1. $1.6\times10^{6}\ \mathrm{J}$
  2. $3.6\times10^{6}\ \mathrm{J}$
  3. $9.1\times10^{6}\ \mathrm{J}$
  4. $1.6\times10^{-19}\ \mathrm{J}$
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Correct answer: (b) $3.6\times10^{6}\ \mathrm{J}$

$1000\ \mathrm{W}\times3600\ \mathrm{s}=3.6\times10^{6}$ J.

3.The consumption of energy by a 60 W bulb in 2 s is: (MDCAT 2022)

  1. 120 J
  2. 60 J
  3. 30 J
  4. 0.02 J
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Correct answer: (a) 120 J

$E=Pt=60\times2=120$ J.

4.One kilowatt-hour is equal to: (MDCAT 2024)

  1. 3.6 J
  2. 3.6 kJ
  3. 3.6 MJ
  4. 36 MJ
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Correct answer: (c) 3.6 MJ

$1\ \mathrm{kWh}=1000\times3600=3.6\times10^{6}$ J, which is 3.6 MJ.

5.An electric motor is used to lift a weight of 2.0 N through a vertical distance of 100 cm in 4 s. What is the power output of the motor? (MDCAT 2024)

  1. 0.25 W
  2. 0.5 W
  3. 0.75 W
  4. 1 W
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Correct answer: (b) 0.5 W

$P=W/t=(2.0\times1.0)/4=0.5$ W.

6.The rate of doing work at any instant of time is called: (KMU MDCAT 2025)

  1. Work done
  2. Instantaneous power
  3. Average power
  4. Mechanical energy
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Correct answer: (b) Instantaneous power

Instantaneous power is the rate of doing work at a given moment.

7.Two students, A and B, each carry a 20kg load to the top of a long staircase. Student A takes 10sec, while student B takes 20sec. Which statement is CORRECT? (KMU MDCAT 2025)

  1. Student A does more work than student B
  2. Student B uses more power than student A
  3. Both students do the same amount of work, but student A uses more power
  4. Student A and B use the same power since they lifted the same weight
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Correct answer: (c) Both students do the same amount of work, but student A uses more power

The same load raised the same height is the same work, and the one who takes half the time delivers twice the power.

8.1 kWh is equal to: (NUMS MDCAT 2025)

  1. 3.6 MW
  2. 3.6 MJ
  3. 3.6 kJ
  4. 3.6 GJ
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Correct answer: (b) 3.6 MJ

A kilowatt for an hour is $1000\times3600$ joules, that is $3.6\,\mathrm{MJ}$.

9.A constant force F acts on a body and displaces it by distance Δd in a time Δt. The rate at which force is doing work is: (SIBA MDCAT 2025)

  1. F x Δd
  2. F x Δt
  3. F x Δd/Δt
  4. F x Δt/Δd
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Correct answer: (c) F x Δd/Δt

Power is work over time, that is $F\Delta d/\Delta t$.

10.An electric motor is used to lift the weight of 2.0N through a vertical distance of 100 cm in 4 sec. What is the power output of the motor? (UHS MDCAT 2024)

  1. 0.25 W
  2. 0.5 W
  3. 0.75 W
  4. 1 W
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Correct answer: (b) 0.5 W

$P=W/t=2\times1/4$, which is $0.5\,\mathrm{W}$.

11.Which of the following pairs correctly matches a physical quantity with its SI unit? (KMU MDCAT 2024)

  1. Energy- Newton
  2. Force- Joule
  3. Power- Watt
  4. Velocity-m/s^2
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Correct answer: (c) Power- Watt

Power is measured in watts; force in newtons and energy in joules.

12.What is the power of electric motor when it performs work of 64 × 106 J in 8 seconds? (NUMS MDCAT 2024)

  1. 6 Kilowatts
  2. 7 Kilowatts
  3. 8 Megawatts
  4. 7 Megawatts
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Correct answer: (c) 8 Megawatts

$P=W/t=64\times10^6/8$, which is $8\,\mathrm{MW}$.

13.Kilowatt hour is a unit of: (SZABMU MDCAT 2023)

  1. Energy
  2. Energy x time
  3. Power
  4. (power)(energy)
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Correct answer: (a) Energy

A kilowatt hour is power times time, that is energy.

14.The unit of power in British engineering system is: (SZABMU MDCAT 2023)

  1. Horse power
  2. Watt
  3. Js-1
  4. Js
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Correct answer: (a) Horse power

The British engineering unit of power is the horsepower.

15.1 Nms-1 = : (SZABMU MDCAT 2023)

  1. 1 Kilo watt hour
  2. 1 J.s
  3. 1 watt
  4. 1 J.s-2
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Correct answer: (c) 1 watt

A newton metre per second is a joule per second, that is a watt.

16.1 kWh = (NUMS MDCAT 2023)

  1. 0.36 × 106 J
  2. 36 × 105 J
  3. 3.6 × 106 J
  4. 0.036 × 105 J
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Correct answer: (c) 3.6 × 106 J

A kilowatt for an hour is $1000\times3600$, that is $3.6\times10^6\,\mathrm{J}$.

17.Power is dot product of: (NUMS MDCAT 2023)

  1. Force and displacement
  2. Force and velocity
  3. Force and time
  4. Work and time
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Correct answer: (b) Force and velocity

Power is the scalar product of force and velocity.

18.For an ideal gas equation PV= nRT, the dimensions of Real Gas Constant R are: (UHS MDCAT 2023)

  1. [M1 L2 T-2 K-1]
  2. [M1 L-3 T-1 K-1]
  3. [M1 L-2 T-1 K-1]
  4. [M1 L-3 T-2 K-1]
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Correct answer: (a) [M1 L2 T-2 K-1]

$R=PV/nT$ is energy per mole per kelvin, that is $[\mathrm{M\,L^2\,T^{-2}\,K^{-1}}]$.

19.A car is moving at a velocity of 50 m/s and then the driver puts the brake and the car comes to rest. The force applied by car in the opposite direction is 2 N. (PMC MDCAT 2022)

  1. -100 watt
  2. 0 watt
  3. 25 watt
  4. 100 watt
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Correct answer: (d) 100 watt

$P=Fv=2\times50$, which is $100\,\mathrm{W}$.

20.A block moves in uniform circular motion because a cord tied to the block is anchored at the center of the circle. What will be the power exerted on the block by the cord? (PMC MDCAT 2022)

  1. Positive
  2. Zero
  3. Negative
  4. variable
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Correct answer: (b) Zero

The cord pulls at right angles to the motion, so it does no work and delivers no power.

21.A block of mass 2 kg is moving with the velocity 5 m/s in the horizontal direction under an influence of force 20 N. How much power is delivered by normal force? (PMC MDCAT 2022)

  1. -100 W
  2. 100 W
  3. 0 W
  4. 200 W
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Correct answer: (c) 0 W

The normal force is at right angles to the motion, so it does no work and delivers no power.

22.1 kilowatt =____________ Watts. (PMC MDCAT 2022)

  1. 2000 watts
  2. 1000 watts
  3. 300 watts
  4. 100 Watts
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Correct answer: (b) 1000 watts

A kilowatt is a thousand watts.

23.A 1kW motor pumps out water from a well 10 meter deep. What is the quantity of water pumped out per second? (PMC MDCAT 2022)

  1. 9.2 kg
  2. 9.5 kg
  3. 10.2 kg
  4. 10.8 kg
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Correct answer: (c) 10.2 kg

$m=Pt/gh=1000/(9.8\times10)$, about $10.2\,\mathrm{kg}$ each second.

24.1hp is equal to: (NUMS MDCAT 2022)

  1. 476 watts
  2. 647 watts
  3. 746 watts
  4. 487 watts
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Correct answer: (c) 746 watts

One horsepower is $746\,\mathrm{W}$.

25.The product of force and velocity is equal to: (NUMS MDCAT 2022)

  1. Kinetic energy
  2. Potential energy
  3. Power
  4. Work done
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Correct answer: (c) Power

Force times velocity is power.

26.Which of the following is not a unit of power? (PMC Practice 2021)

  1. Horse power
  2. Kilowatt
  3. kWh
  4. Nm/s
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Correct answer: (c) kWh

A kilowatt hour is power times time, that is energy.

27.One kilowatt-hour is commonly termed as one commercial unit of electric energy which is equal to: (PMC MDCAT 2020)

  1. 3.6 x 105 J
  2. 3.6 x 106 J
  3. 3.6 x 104 J
  4. 3.6 x 103 J
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Correct answer: (b) 3.6 x 106 J

A kilowatt for an hour is $1000\times3600$, that is $3.6\times10^6\,\mathrm{J}$.

28.An automobile is moving forwards with uniform velocity due to the force exerted by its engine. If the force is doubled with the velocity remaining constant what happens to its total power? (UHS MDCAT 2019)

  1. It is squared
  2. It is halved
  3. It is doubled
  4. It does not change
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Correct answer: (c) It is doubled

$P=Fv$, so at the same speed twice the force is twice the power.

29.Energy consumed by 60 watt bulb in 2 minutes is equal to: (UHS MDCAT 2018)

  1. 7.2 kilo joules
  2. 720 joules
  3. 120 joules
  4. 72000 joules
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Correct answer: (a) 7.2 kilo joules

$60\times120$ is $7200\,\mathrm{J}$, that is $7.2\,\mathrm{kJ}$.

30.The rate at which work is being done is called: (UHS MDCAT 2018)

  1. Power
  2. Energy
  3. Density
  4. Force
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Correct answer: (a) Power

The rate of doing work is power.

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