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

Rajshahi Board 2021

At what velocity will the momentum and the kinetic energy of a body have the same value?

Think it through first, then pick an option.

  1. a 4 m/s
  2. b 2 m/s
  3. c 1/2 m/s
  4. d 1/4 m/s
Answer and explanation

Correct answer: b 2 m/s

Momentum is p = mv (Chapter 3) and kinetic energy is ½mv². From mv = ½mv² the mass cancels and v = 2 m/s. The two are equal in number only in these units (kg, m/s).

Why the other options are wrong

  • a 4 m/s: This is not the answer: Momentum is p = mv (Chapter 3) and kinetic energy is ½mv². From mv = ½mv² the mass cancels and v = 2 m/s. The two are equal in number only in these units (kg, m/s).
  • c 1/2 m/s: This is not the answer: Momentum is p = mv (Chapter 3) and kinetic energy is ½mv². From mv = ½mv² the mass cancels and v = 2 m/s. The two are equal in number only in these units (kg, m/s).
  • d 1/4 m/s: This is not the answer: Momentum is p = mv (Chapter 3) and kinetic energy is ½mv². From mv = ½mv² the mass cancels and v = 2 m/s. The two are equal in number only in these units (kg, m/s).