Using energy considerations, calculate the average force a 60.0-kg sprinter exerts backward on the track to accelerate from 2.00 to 8.00 m/s in a distance of 25.0 m, if he encounters a headwind that exerts an average force of 30.0 N against him.

F = 102 N

Explanation:

ASSUMING the track is horizontal to avoid gravity potential energy considerations.

The work of the applied force must overcome friction work and increase the kinetic energy of the runner

F(d) = Ff(d) + ½m(v² - u²)

F = Ff + m(v² - u²) / 2d

F = 30.0 + 60.0(8.00² - 2.00²) / (2(25.0))

F = 102 N

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