Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Lose weight or train?

  1. Jan 26, 2009 #1
    EDIT -- I posted this here because I figured its more of a conceptual problem than a HW problem, but if people see otherwise, feel free to delete the post.

    I'm having troubles wrapping my head around this one (I've provided the example from my class notes below):

    My question -- how does a decrease in the mass of the rider increase his power producing ability by 18 W? Intuitively, I would think that a rider with lower mass will experience less resistive forces when riding (i.e., gravity when on an incline, kinetic friction) and so can sustain the same velocity as a heavier rider without applying as much force and, therefore, less power.

    From a physics standpoint, how does a mass decrease result in an increase in Power as this example suggests (taken from my class notes)?

    Last edited: Jan 26, 2009
  2. jcsd
  3. Jan 26, 2009 #2


    User Avatar
    Homework Helper

    "Rider"? Climber would be a better description, the riders weight is being treated as the opposing force in this problem.
  4. Jan 26, 2009 #3
    I dont think our bodies are that simple to derive power from the ratio of masses. It seems ridiculous. Even this 250 watt cannot be sustained forever. A cheetah-at it's max speed- should stop pursuing the deer within 40 seconds or so before it gets hyperthermia. :)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook