Energy and Kinetic Energy

Energy and Kinetic Energy MDCAT MCQs with answers

20 past paper MCQs on Energy and Kinetic Energy, 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.

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1.A particle of mass $m$ at rest is acted upon by a force $P$ for a time $t$. Its kinetic energy after time $t$ is: (MDCAT 2022)

  1. $P^2t^2/m$
  2. $P^2t^2/2m$
  3. $P^2t^2/3m$
  4. $P^2t^2/4m$
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Correct answer: (b) $P^2t^2/2m$

The impulse gives $p=Pt$, and $E_k=p^2/2m=P^2t^2/2m$.

2.An 8.0 kg box slides along a horizontal frictionless floor at $3\ \mathrm{m\,s^{-1}}$ and meets a light spring that compresses 12 cm before the box stops. Calculate the retarding force of the spring. (MDCAT 2023)

  1. 3 N
  2. 30 N
  3. 300 N
  4. 3000 N
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Correct answer: (c) 300 N

$\tfrac{1}{2}mv^2=\tfrac{1}{2}(8)(3)^2=36$ J, and $F=W/d=36/0.12=300$ N.

3.Two bodies with kinetic energies in the ratio 4 : 1 are moving with equal linear momentum. The ratio of their masses is: (MDCAT 2023)

  1. 1 : 4
  2. 4 : 1
  3. 1 : 2
  4. 2 : 1
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Correct answer: (a) 1 : 4

With $p$ equal, $E_k=p^2/2m$, so the kinetic energy is inversely proportional to the mass.

4.If P is the momentum of an object and m is its mass, then its kinetic energy is: (UHS MDCAT 2025)

  1. P/2m
  2. P^2/2m
  3. 1/2 Pm^2
  4. 1/2 P^2/m^2
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Correct answer: (b) P^2/2m

From $p=mv$, $v=p/m$, so $K=\tfrac12 mv^2$ becomes $p^2/2m$.

5.Earth receives large amount of energy directly from: (UHS MDCAT 2025)

  1. Wind
  2. Water
  3. Sun
  4. Moon
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Correct answer: (c) Sun

Sunlight is the energy the Earth receives directly; wind and water carry it only after it has arrived.

6.A 0.5 kg ball moving at 6 m/s has kinetic energy (UHS MDCAT 2025)

  1. 9 J
  2. 18 J
  3. 6 J
  4. 3 J
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Correct answer: (a) 9 J

$K=\tfrac12\times0.5\times6^2$, which is $9\,\mathrm{J}$.

7.If velocity is doubled, what happens to kinetic energy: (NUMS MDCAT 2025)

  1. Remains same
  2. Doubles
  3. Quadruples
  4. Halves
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Correct answer: (c) Quadruples

$K=\tfrac12mv^2$ goes as the square of the speed, so twice the speed is four times the energy.

8.The work done on a body is stored in it in the form of: (SZABMU MDCAT 2025)

  1. Power
  2. Energy
  3. Momentum
  4. Impulse
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Correct answer: (b) Energy

The work done on a body appears as its energy.

9.The relation between K.E and momentum P is given by: (NUMS MDCAT 2024)

  1. K.E = 1/2 P/M
  2. K.E = 1/2 P/M2
  3. K.E = 1/2 P2/M2
  4. K.E = 1/2 P2/M
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Correct answer: (d) K.E = 1/2 P2/M

From $p=mv$, the kinetic energy $\tfrac12mv^2$ becomes $p^2/2m$.

10.A particle of mass m at rest is acted upon by a force P for time t. Its kinetic energy after time t is: (UHS MDCAT 2023)

  1. (P^2 t^2)/m
  2. (P^2 t^2)/2m
  3. (P^2 t^2)/3m
  4. (P^2 t^2)/4m
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Correct answer: (b) (P^2 t^2)/2m

The impulse $Pt$ is the momentum gained, and $K=p^2/2m$ gives $P^2t^2/2m$.

11.The unit of kinetic energy is same as that of: (SZABMU MDCAT 2023)

  1. Work
  2. Power / Time
  3. Time / Power
  4. Work / Time
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Correct answer: (a) Work

Kinetic energy is measured in joules, the same unit as work.

12.A car of mass 800 Kg accelerates from 20m-1 to 30ms-1, the increase in K.E is: (SZABMU MDCAT 2023)

  1. 2 J
  2. 200 KJ
  3. 200 J
  4. 2 KJ
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Correct answer: (b) 200 KJ

$\tfrac12\times800\times(30^2-20^2)$ is $200\,\mathrm{kJ}$.

13.A body of mass 'm' is moving with velocity 'v'. After a short interval of time its velocity becomes double. How many times its K.E will increase or decrease? (NUMS MDCAT 2023)

  1. 2 time increased
  2. 2 time decreased
  3. 4 time increased
  4. 4 time decreased
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Correct answer: (c) 4 time increased

$K=\tfrac12mv^2$ goes as the square of the speed, so doubling it gives four times the energy.

14.An 8.0-kg box slides along a horizontal frictionless floor at 3 m/s and collides with a relatively massless spring that compresses 12 cm before the box comes to a rest. Calculate the retarding force of the spring. (UHS MDCAT 2023)

  1. 3N
  2. 30N
  3. 300N
  4. 3000N
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Correct answer: (c) 300N

The kinetic energy $\tfrac12\times8\times3^2=36\,\mathrm{J}$ is absorbed over $0.12\,\mathrm{m}$, so the force is $300\,\mathrm{N}$.

15.A ball is projected with kinetic energy E at 45 degree angle. At the highest point its kinetic energy is: (PMC MDCAT 2022)

  1. 2E
  2. 0
  3. E
  4. E/2
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Correct answer: (d) E/2

Only the horizontal component is left at the top, and at $45^{\circ}$ that carries half the energy.

16.The K.E. of object at rest Is: (PMC MDCAT 2022)

  1. Maximum
  2. Negative
  3. Zero
  4. Constant
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Correct answer: (c) Zero

$K=\tfrac12mv^2$, and at rest the speed is zero.

17.Minimum value of kinetic energy is: (PMC MDCAT 2022)

  1. Infinite
  2. Zero
  3. Negative constant
  4. Minus infinite
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Correct answer: (b) Zero

Kinetic energy is $\tfrac12mv^2$ and can never fall below zero.

18.If the kinetic energy is increased 4 times then momentum will increase: (PMC MDCAT 2022)

  1. 3 times
  2. 4 times
  3. 5 times
  4. 2 times
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Correct answer: (d) 2 times

$p=\sqrt{2mK}$, so four times the kinetic energy doubles the momentum.

19.A car and a train both have same kinetic energy. Which one has greater momentum? (PMC MDCAT 2022)

  1. Car
  2. Train
  3. Both have same
  4. No change
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Correct answer: (b) Train

$p=\sqrt{2mK}$, so at the same kinetic energy the heavier body carries the greater momentum.

20.When the speed of your car is halved, by what factor does its kinetic energy decreases? (PMC MDCAT 2020)

  1. ½
  2. ¼
  3. ⅛
  4. ⅙
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Correct answer: (b) ¼

$K$ goes as the square of the speed, so half the speed leaves a quarter of the energy.

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