An athlete of mass 60 kg runs at 5 m/s. What is the kinetic energy gained compared to standing still?
750 J
Kinetic energy is given by \(KE = \tfrac{1}{2}mv^{2}\), where m is mass and v is velocity.
Substituting m = 60 kg and v = 5 m/s: \(KE = \tfrac{1}{2} \times 60 \times 5^{2}\).
This gives \(KE = \tfrac{1}{2} \times 60 \times 25 = 750\) joules.
At rest the velocity is zero, so the resting kinetic energy is zero and the entire 750 J is the energy gained.
Hence, the kinetic energy gained is 750 J.
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