# Lose weight or train?

1. Jan 26, 2009

### Byrne

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)?

Thanks!

Last edited: Jan 26, 2009
2. Jan 26, 2009

### rcgldr

"Rider"? Climber would be a better description, the riders weight is being treated as the opposing force in this problem.

3. Jan 26, 2009

### sganesh88

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. :)