A body of mass 5 kg moves at 4 m s-1. Its kinetic energy is
Correct answer: C. 40 J
- A. 10 J
- B. 20 J
- C. 40 J
- D. 80 J
Explanation
Kinetic energy is half times 5 times 4 squared, which is half times 5 times 16, giving 40 J. The common slip is to forget to square the velocity, which gives 10 J, or to forget the factor of one half, which gives 80 J.
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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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