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Work and Energy

20 free MDCAT Physics MCQs on Work and Energy (PM&DC syllabus), each with the answer, an explanation and the textbook line it comes from. Tap to check, no sign-up.

MDCAT (Pakistan)PhysicsPre-medical (Grade 12)20 questions

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  1. Question 1

    The gravitational force per unit mass on a body is called the:

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    Answer: A) Gravitational field strength

    SI unit N/kg. Source: PHYSICS 11 KPK (taleem360.com), p. 123.

  2. Question 2

    The escape velocity from the Earth's surface is about:

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    Answer: D) 11.2 km/s

    v = sqrt(2 g R). Source: PHYSICS 11 KPK (taleem360.com), p. 136.

  3. Question 3

    With g = 1.6 m/s2 and radius 1.74 x 10^6 m, the escape velocity from the Moon is about:

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    Answer: A) 2.36 km/s

    v = sqrt(2 x 1.6 x 1.74 x 10^6) = 2.36 x 10^3 m/s. Source: PHYSICS 11 KPK (taleem360.com), p. 137.

  4. Question 4

    The average power of a man walking upstairs at an ordinary speed is only about:

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    Answer: D) 0.33 kW

    About the energy of 0.33 litre of petrol is eaten as food per day. Source: PHYSICS 11 KPK (taleem360.com), p. 128.

  5. Question 5

    A suitcase is pulled 4.90 m along level ground by a 16.8 N force at 30 to the horizontal. The work done by the pull is:

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    Answer: B) 71.3 J

    W = F d cos 30 = 16.8 x 4.9 x 0.866 = 71.3 J; friction does -0.833 J. Source: 11 Physics Book FBISE, p. 80.

  6. Question 6

    A machine uses 1000 J of energy to raise a 10 kg block through 6.0 m. Its efficiency is:

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    Answer: D) 58.8%

    Output = mgh = 588 J; 588/1000 = 58.8%. Source: PHYSICS 11 KPK (taleem360.com), p. 132.

  7. Question 7

    A 5000 kg load is lifted 30 m in 2 minutes. The power used is about:

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    Answer: A) 12.26 kW

    W = mgh = 1 471 500 J; P = W/t = 1471500/120 = 12 262.5 W. Source: PHYSICS 11 KPK (taleem360.com), p. 128.

  8. Question 8

    The work needed to stop a 1500 kg car moving at 40 km/h is about:

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    Answer: A) 92.6 kJ

    v = 11.1 m/s; W = 1/2 x 1500 x 11.1^2 = 92.6 kJ. Source: 11 Physics Book FBISE, p. 87.

  9. Question 9

    The work done by a force perpendicular to the displacement is:

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    Answer: B) Zero

    cos 90 = 0. Source: 11 Physics Book FBISE, p. 79.

  10. Question 10

    A person pushes hard on a cart that does not move. No work is done because the:

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    Answer: D) Displacement is zero

    W = F d cos theta with d = 0. Source: PHYSICS 11 KPK (taleem360.com), p. 120.

  11. Question 11

    The area under a force-displacement graph gives the:

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    Answer: A) Work done

    For a variable force it is the area under the F cos theta vs d curve. Source: 11 Physics Book FBISE, p. 79.

  12. Question 12

    One joule is the work done when a force of 1 N displaces a body by:

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    Answer: B) 1 m in its direction

    1 J = 1 N m. Source: PHYSICS 11 KPK (taleem360.com), p. 121.

  13. Question 13

    In a conservative field, the work done in moving a body between two points:

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    Answer: C) Is independent of path

    Also, the work done around a closed path is zero. Source: 11 Physics Book FBISE, p. 81.

  14. Question 14

    Which of these is a conservative force?

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    Answer: D) Gravitational force

    Electric force is also conservative. Source: 11 Physics Book FBISE, p. 81.

  15. Question 15

    Which of these is a non-conservative force?

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    Answer: A) Frictional force

    Work against friction depends on the path followed. Source: 11 Physics Book FBISE, p. 81.

  16. Question 16

    In machines, energy lost to friction between moving parts appears mainly as:

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    Answer: D) Heat

    This is why practical efficiency is below 100%. Source: PHYSICS 11 KPK (taleem360.com), p. 130.

  17. Question 17

    The efficiency of an ideal machine is:

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    Answer: A) 100%

    Real machines are always less than 100% efficient. Source: PHYSICS 11 KPK (taleem360.com), p. 129.

  18. Question 18

    For absolute potential energy, the zero point is taken at a point:

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    Answer: A) Very far from the Earth

    There the force of gravity is negligible. Source: PHYSICS 11 KPK (taleem360.com), p. 132.

  19. Question 19

    When a body falls through air, its loss in potential energy equals:

    Show answer and explanation

    Answer: B) Gain in KE + work against friction

    mgh = 1/2 m v^2 + f h. Source: PHYSICS 11 KPK (taleem360.com), p. 138.

  20. Question 20

    The cleanest form of fossil fuel, which burns completely and leaves no ash, is:

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    Answer: A) Natural gas

    Coal burning causes significant atmospheric pollution. Source: PHYSICS 11 KPK (taleem360.com), p. 141.

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