Lesson: Chapter 18 — Work, Energy and Power

18.2. Kinetic energy 6 of 7 Reset answers

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Question 6

An object of mass 500 g is moving at a certain velocity, and at that moment its kinetic energy is 9 J. What is its velocity? (Exercise 18.2, part 2)

A 6 m s^-1 B 4.2 m s^-1 C 36 m s^-1 D 0.19 m s^-1

The right answer is the one marked above.

6 m s^-1. 500 g is 0.5 kg, so 9 = ½ × 0.5 × v² = 0.25 v². Then v² = 36 and v = 6 m s^-1.

0.19 m s^-1 comes from putting 500 into the formula instead of 0.5. The formula takes kilograms, so grams must be divided by 1000 first.

Answer the question to continue.