# :o 'Vette not the best bang for the buck :o

Discussion in 'American Cars' started by naranhito, Jun 2, 2007.

1. Sprinting flights of stairs isn't the same. A thoroughbred can produce like 7 or 8 hp but only for a mile or so. 1hp is what a horse can sustain for a long time, I think on a bicycle I can sustain the equivalent of .75hp for a long time.

Edit: I'd be wrong though. According to wikipedia a first class athlete can sustain 500W for about 30 minutes, and that's .67hp...

Okay. I tried to work it out. Assuming a fit person can sustain about 7 m/s (25 km/h) then they would be expanding energy (ignoring losses) of:

kg* (7^2 / 1^2)= mass*49
=3765 joules

1 watt = 1 joule per second
Therefore power = 3.765 kW

which obviously can't be right.

2. The figure I often hear quoted is that fit humans can sustain approximately .33hp with their leg muscles for a reasonable amount of time.

However, I know that Burt Rutan's human powered plane was calibrated to run on like .4 hp, so that sort of makes sense.

3. you are aware that 1 HORSE power is not actually measured by horses and was more of an estimate then anything else. there is much debate over how James Watt actually came to the figure of 33,000 ft·lbf/min as "horsepower"

anyhow:
"Put into perspective, a healthy human can produce about 1.2 hp briefly and sustain about 0.1 hp indefinitely, and trained athletes can manage up to about 0.3 horsepower for a period of several hours."

also im having a tough time following your logic. you're trying to figure out how much energy you're using to kepp yourself going at 25km/h by only figuring your mass

FIRST of all, mass shouldnt even be in the equation.
SECOND, ideally it would require 0 energy to keep you moving, but you're fighting air resistance and mechanical resistance, neither of which are present in your equation[?] and i dont even know how you would go about calculating that without experimentation.

man, who taught you physics?

edit: this is why when i tested my own HP, i was using stairs because i could calculate the height i climbed and used that and the time it took me to do so along with my mass to calculate the power i was putting down

4. Burt Rutan did not make a human powered airplane to my knowledge. I believe you are talking about the gossomer albatros.

5. Actually, looking back at my photos from the Smithsonian, you're correct. But anyway, .75 hp is rediculous to use as a figure for sustained use.

6. Yea, your math is wrong. I think you are actually calculating how much power it would take to accelerate that mass to that velocity, not how much to overcome drag.

7. I love where this thread went. I can probably only produce like .000473 HP because I get no physical exercise at all, smoke, and eat nothing but horrible food. It'd gonna be rad when I die at 34.

8. thats insane.

9. lolwut

10. (210 / 3241)x 10000 / 22547 x 100000= 2837

Eclipse > Z06