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MCQ practice · SSC Physics Board questions · Chapter 4: Work, Power and Energy

Sylhet Board 2022

The kinetic energy of a moving body will become four times if-

  1. i. the velocity is doubled
  2. ii. both the velocity and the mass are doubled
  3. iii. the velocity is doubled and the mass is halved

Think it through first, then pick an option.

  1. a i
  2. b ii
  3. c i and ii
  4. d ii and iii
Answer and explanation

Correct answer: a i

i true: Doubling the velocity gives 2² = 4 times the energy. ii false: Doubling both velocity (×4) and mass (×2) gives 8 times, not 4 times. iii false: Doubling the velocity (×4) and halving the mass (×1/2) gives 2 times, not 4 times.

Why the other options are wrong

  • b ii: This is not the answer; the right combination is i. i true: Doubling the velocity gives 2² = 4 times the energy. ii false: Doubling both velocity (×4) and mass (×2) gives 8 times, not 4 times. iii false: Doubling the velocity (×4) and halving the mass (×1/2) gives 2 times, not 4 times.
  • c i and ii: This is not the answer; the right combination is i. i true: Doubling the velocity gives 2² = 4 times the energy. ii false: Doubling both velocity (×4) and mass (×2) gives 8 times, not 4 times. iii false: Doubling the velocity (×4) and halving the mass (×1/2) gives 2 times, not 4 times.
  • d ii and iii: This is not the answer; the right combination is i. i true: Doubling the velocity gives 2² = 4 times the energy. ii false: Doubling both velocity (×4) and mass (×2) gives 8 times, not 4 times. iii false: Doubling the velocity (×4) and halving the mass (×1/2) gives 2 times, not 4 times.