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From Cecil's Mailbag by the Straight Dope Science Advisory Board

Does it take more energy going downstairs than up?

Dear Straight Dope:

I have a dispute with my
significant other. She claims that going *down* stairs takes more energy
than going up stairs. At first glance, anyone can see that this is
clearly wrong ... or is it? She says that when you go down stairs, you
have to absorb the energy from gravity pulling you down, and that takes
energy on your behalf. I give her the argument that I get much more tired
going up 50 flights of stairs than down! Please help us to settle this,
Cecil, once and for all. We will be forever in your debt. --Drew Mazurek, North Haven, CT


SDSTAFF Dex replies:


"Absorb the energy"?? Some confusion here, methinks. Since the force of gravity naturally tends to pull things down, you need to exert MORE force than that to lift things up. A round rubber ball at the top of stairs needs only a mild, tiny push to get it to start rolling down the stairs ... but it needs an energy-laden throw to get it to go up the stairs.


So it takes more energy to go up (counter to gravity) than to go down (letting gravity do most of the work.)


Now, I think (although it's unclear) that your squeeze is arguing that you have to exert force in walking downstairs, to prevent gravity from just pulling you all the way down with a splat. Yeah, well, OK, but that's the force you're exerting to walk upright rather than just roll down the stairs. You need to exert that same force in going up the stairs too, just to stand on your feet.


Sheesh, some of the questions we get.


--SDSTAFF Dex

Straight Dope Science Advisory Board

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