Lesson: Chapter 18 — Work, Energy and Power

18.2. Kinetic energy 5 of 7 Reset answers

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Question 5

A dog has a mass of 10 kg. At what velocity is the dog running when its kinetic energy is 20 J? (Exercise 18.2, part 1)

A 2 m s^-1 B 4 m s^-1 C 0.5 m s^-1 D 40 m s^-1

The right answer is the one marked above.

2 m s^-1. 20 = ½ × 10 × v², so 20 = 5 v², so v² = 4 and v = 2 m s^-1.

4 m s^-1 is v², not v. Running the formula backwards means you must remember to take the square root at the end.

Answer the question to continue.