When the speed of a moving body is doubled then___________________?
Correct answer: D. its momentum is doubled
- A. its K.E is doubled
- B. its acceleration is doubled
- C. its P.E is doubled
- D. its momentum is doubled
Explanation
Momentum is p = mv, so doubling the speed while keeping mass constant doubles the momentum. Kinetic energy is K = 1/2 mv2, so it becomes four times larger, not merely twice as large. Students may choose a by treating kinetic energy as directly proportional to speed instead of speed squared.
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About Kinetic Energy
Kinetic energy is the energy of motion, given for a nonrelativistic object by K = ½mv², so it depends on mass and the square of speed. Questions connect kinetic energy with work through the work energy theorem, calculate changes in kinetic energy, and distinguish it from momentum and potential energy.
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