Question Part Points Submissions Used A 68.5-kg runner has a speed of 5.80 m/s a

Question

Question Part Points Submissions Used A 68.5-kg runner has a speed of 5.80 m/s at one instant during a long-distance event. (a) What is the runner's kinetic energy at this instant?
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(b) If he doubles his speed to reach the finish line, by what factor does his kinetic energy change? KEf KEi = Question Part Points Submissions Used Question Part Points Submissions Used Question Part Points Submissions Used Question Part Points Submissions Used Question Part Points Submissions Used A 68.5-kg runner has a speed of 5.80 m/s at one instant during a long-distance event. (a) What is the runner's kinetic energy at this instant?
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(b) If he doubles his speed to reach the finish line, by what factor does his kinetic energy change? KEf KEi = A 68.5-kg runner has a speed of 5.80 m/s at one instant during a long-distance event. (a) What is the runner's kinetic energy at this instant?
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(b) If he doubles his speed to reach the finish line, by what factor does his kinetic energy change? KEf KEi = (a) What is the runner's kinetic energy at this instant?
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(b) If he doubles his speed to reach the finish line, by what factor does his kinetic energy change? KEf KEi = KEf KEi = Question Part Points Submissions Used

Explanation / Answer

m = 68.5 kg
v = 5.80 m/s
(a) What is the runner's kinetic energy at this instant?
KE = 1/2 mv^2 = 1/2 (68.5 Kg) (5.80 m/s)^2
KEi = 1152.17 N-m or Joules.

(b) If he doubles his speed to reach the finish line, by what factor does his kinetic energy change?

KEf / KEi = [1/2 m (2vi)^2] / [1/2 m vi^2 ]

KEf / KEi = 4

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