Why Riding A Bicycle Requires Less Energy Than Going Afoot?

The extra energy of walking is dissipated as heat in bouncing up and down on the surface being walked upon. (Among other things?)

But one can hold oneself evenly while walking, controlling any bouncings, still be more tired than the rider.

In which aspect may there be involved the force of gravitation utilized by bycicle construction?

They do not do the same amount of work, if they are on level ground there is no externally measurable work done, the cyclist can cruise while not doing any work, the walker cannot.

You can not walk and hold yourself level, you must lift your feet and legs with each step.

How do you know, "but spends less energy riding." is true?

To Passingtongreen

The same amount of work was meant in the sense a walker and a bycyclist get themselves from point A to point B (same distance), in the same amount of time.

To Lyn

Try walking and another time riding (on a good road), not speeding too fast, the same distance, let's say 10 miles, and see the difference.

Your definition of work is..............................._{he searches for a non-confrontational term}..............un-scientific, at best.

You have no factual basis for your remarks.

AP #1,

You gotta watch trying to compare biological work to mechanical work. Just for example, you use about 0.1 kWhr sitting on your front porch watching the grass grow. That rock you use for a door stop doesn't do any work just sitting there.

Even if you could keep your body level while walking (you can't, but the mechanics are too much for me on a Sunday), your legs are moving, so the cg of your body is going up and down even if the cg of your torso isn't.

Grocho Marx could walk without his body going up and down...just bend your knees more.

Bicycling uses less calories per hour than walking fast because of the gearing...unless you try to ride slow in top gear sitting down.

Leisure cycling @ about 10mph......300 calories an hour

Walking very briskly @ 4mph..........400 calories an hour

Even if you control up and down, you still must accelerate forward and backward.

Tornado has the correct answer. Work done is F•ds, (where F is force [mg] and ds is displacement) and in this case the walker performs work (thus expends energy) every time he lifts a foot. He gains very little of that energy back as he lowers his foot after taking a step. (Yes he might try to maintain a 'roughly' constant center of gravity above the ground and reduce the net work done, but that's an unnatural way of walking and probably burns a lot of muscle energy.)

The bicyclist, on the other hand, only has to overcome a bit of static fiction and rolling friction; he performs very little work against gravity since the ds part of F•ds is nearly zero as his feet maintain the same average distance from the ground as he pedals, and his center of gravity barely moves.

Consider also, the walkers legs are holding his weight up. When walking smoothly without bouncing your torso you legs will usually compensate for the motion by being bent, at which time your muscles are carrying your mass; when walking normally (bouncing) your bones tend to carry most of your mass. When you are on a bicycle, most of your mass is resting on the seat, one leg is resting on the pedal while the other is using the muscles to push the pedal downward (mass is negated by one leg mass riding up while the other is falling with pedal).

So, when walking you are holding your mass up, when riding your mass is resting on the seat.

Drew K

This has to be a GA. Strange that someone thought it was OT, it takes all kinds i guess.

i don't understand of course, but the images are awesome !

Btw, what is the difference in the energies spent by an exerciser on a treadmill vs on a bicycle (spelling ok?) ?

Googling shown it is all about just leverages and force multiplication ("simple machine").

A more effective moving the body is probably not a right explanation.

Sorry, so, it is both : the system of leverages, and a more effective use by the rider of the movements of his body.

You people have forced me to rethink this mechanical advantage thing. I was not taking into account the amount of energy required to overcome gravity while walking.

I'm in the middle of replacing my 30 year old pool pump, on a holiday weekend.

That's enough trauma for now, but I see the light.

Cheers.

If you got 30 years out of a pool pump you should not be feeling any trauma at all...you should be saying to yourself, "I got more than my money's worth out of this one!"

Thank you all, now I know (and many others will know) !