Question

Calculate the power output in watts and horsepower of a shot-putter who takes 1.20 s to accelerate the 7.27-kg shot from rest to 14.0 m/s, while raising it 0.800 m. (do not include the power produced to accelerate his body.)

Answer 1

641.26 watt

0.86 HP

Step-by-step explanation:

1) Power = work done / time

2) Work done = ΔEnergy

3) ΔEnergy = ΔKinetic Energy + ΔPotential enegy

4) ΔKinetic Energy = (1/2)m [Vf² - Vi²] = (1/2) × 7.27 kg (14.0m/s)² = 712.46 J

5) ΔPotential Energy = mgΔh = 7.27kg × 9.81 m/s² (0.800m) = 57.05 J

6) Work done = 712.46J + 57.05J = 769.51J

7) Power = 769.51J / 1.20s = 641.26 watt

8) To find the power in horse powers use the conversion factor

1 horsepower = 745.7 watt

⇒ 641.26 watt × 1 horsepower / 745.7 watt = 0.86 HP