Treadmill: find the work output
a 60 kg subject walks at a speed of 3.5 mph at a 3.5% grade/incline for 15 min.
a 75 kg subject runs at a speed of 6.0 mph at a 0% grade/incline for 30 min.

power = 32.09 watt

work done = 28854 J

Explanation:

a) mass of subject = 60 kg speed = 3.5 mph = 5.63 kph = 1.564 m/s

grade = 3.5%  time= 15 min

tan θ = 0.035

θ = 2°

power = F × v

           = mg sin θ  × v cos Φ

           = 60 × 9.8 × sin2° × 1.564 × cos 180°

           = -32.09 watt

work done = power × time

                  =   28854 J

b) in this part work done is equal to zero.

because the angle between the motion of subject and the force acting is 90° hence cos 90° equals to zero so, work done equal to zero.

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