Using energy considerations, calculate the average force a 60.0 kg sprinter exerts backward on the track to accelerate from 2.00 to 6.00 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.

Answer 1

W=KE2-KE1
=1/2*mv^2 - 1/2*mv^2
= 30kg(6m/s)^2 - 30kg(2m/s)^2
=1080 - 120
=960

W=(Fe - 30N)*d=960
(Fe - 30)25=960
25Fe - 750=960
25Fe=1710
Fe=68.4N