Energy, work &power physics help!!?

50. While running, a person dissipates about 0.60 J of mechanical energy per step per kilogram of body mass. If a 60-kg person develops a power of 70 W during a race, how fast is the person running? Assume a running step is 1.5 m long.

51. Water flows over a section of Niagara Falls at the rate of 1.2 * 10^6 kg/s and falls 50 m (Fig P5.51). How much power is generated by the falling water?

show me step by step how to get the answer plz

ty :D

2 Answers

Relevance
  • 1 decade ago
    Best Answer

    (50) Want to get to m/s:

    .6J/(step)(kg)* 60 kg = 36J/step

    (36J/step) * (1 step)/ 1.5 meters =24J/m

    70w=70J/s

    Vel=(70J/s )*(1m/24J)=2.916m/s

    (51) power=energy/time

    potential energy=mass*gravity acceleration*height

    We don't have mass but we have mass/s, which is good enough because if we pick a time, say 10 secs worth of water, then we would have to divide by 10 anyway to get the power.

    power=(1.2*10^6)(9.8)(50)=5.88*10^8 J/s

    Check the math, etc. It's been a while...

  • bigby
    Lv 4
    3 years ago

    completely accept as true with ryan obes! and that i've got been given an A too! yet anyhow... artwork= stress x distance moved interior the direction of stress potential= artwork completed, artwork= potential transferred potential=artwork completed/ time = potential transferred/ time Plus a lot extra! those are only the main difficulty-loose ones!

Still have questions? Get your answers by asking now.