# Physics/Health/Exercise question

A different forum I participate on (here ) posted the question below. Not sure we are finding and answer over there so figured to throw it to the teeming masses and see what they think.

Any ideas?

The equation for work is for appyling a force through a distance, in the direction of velocity. Just because you support your own weight while walking a distance does not mean you can say W = F * d where F is the force of gravity on your body. The force is not in the same direction as the movement.

Where this equation is appropriate are things like lifting an elevator up 10 stories. Work is force (the weight up the elevator and contents) and the distance is 10 stories (in the exact opposite direction of the force of gravity).

To determine energy expended in walking, you would have to take a bunch of stuff into account, like friction, the bobbing motion of the body (you use less energy if you can keep your center of gravity at the same height), and other stuff. I don’t think it’s really feasible to come up an equation that takes all the variables into account.

Calorie consumption for activities is, I think, usually determined more empirically by measuring the biological processes, rather than using physics on paper.

CookingWithGas is, as usual, right. Now, if you climbed up a ladder 3 miles high, then you’d expend that much elevating your body. Well, somewhat less, I guess, because you’d weigh a lot less by the time you finished that job, given the inefficiencies of human activity and the amount of sweating you’d do, especially if you looked down.

The other thing you have to keep in mind is that people vary tremendously in many biological parameters, including their ability to use stored chemical energy for producing work. That’s why I don’t place too much faith in the figures you see for calories expended during various activities.

Thank you very much! :o

If I looked down from a ladder 3 miles up, I would expend at least 200 calories just by the screaming.

Whack-a-Mole,

W=Fxd

You do have to move your weight forward, so the force you want to know is forward as well, not down.

F=ma

in which m = is your mass in kg
and a = - (the resistance forces acting on you, like air resistance, ground resistance, etc…), basicly everything that pushes you back, contrary to where you’re going.

Now just by standing you’re also burning calories, but they aren’t easy to calculate, cause the bones make the standing up much easier than it would be without them. They’re like pillars supporting our body, saving us a lot of calories.

And finally there are wastes, calories lost in the biological processes.

Try to find out how those kind of charts are built… maybe some of them are built by experts who take in acccount all this who knows