OK, a plain ol’ regular playground seesaw? What’s the typical length for a playground seesaw at an elementary school, maybe ten feet from fulcrum to either end? This pic on Wikipedia look sabout right.
How much does the urine in one evacuation weight? 1 pint equals about half a liter, so 500 grams, so ~ 1 pound of urine. Unload one pound of urine from its location ten feet away from the pivot, and you’ve decreased the torque on that end of the seesaw by 1# x 10’ = ten foot-pounds.
So the fundamental question is this: on a typical playground seesaw, is the friction torque on the pivot bearing typically less than 10 foot pounds? IMHO it’s going to vary somewhat, but in most cases, I’d guess no. I think the typical seesaw pivot is just a short length of pipe riding on the exterior of a cross-bar (see pic at above link), and if you’re lucky, it’s not too rusty and maybe there’s a bit of grease in there. That’ll take more than 10 foot-pounds to get it moving.
In that case they could just add more counterweight. There is no reason why the counterweight has to exactly match the weight of the pisser. I don’t really see why they couldn’t get this to work. You just keep adding to the counterweight until the see-saw just tips over. Remove a half pound from the counterweight and let the urine flow.
Thanks to those who have done some math. I have no tools to check your work but I have faith that if they were totally off someone would have jumped at them.
Are those two rolls of quarters in your pocket our are you really really happy to see me?.
Yet further proof that nobody actually understands the American system of units: You just had to convert into metric and back, using two approximations, to come up with the result that a pint of water weighs a pound, which is one of the design features of the system.
You’re missing the point. Even if the pisser decreases his weight so he is a pound lighter than the counterweight, he still has to overcome the friction of the fulcrum to allow the see-saw to move. If the maximum weight one can lose in a single piss is one pound, and the torque friction on the fulcrum is greater than ten foot-pounds, then the see-saw will not move. (Assuming a ten-foot see-saw.)
You can overcome this by using a longer see-saw and/or one with a higher-quality bearing. Neither of which are likely to be found on an average playground.
Let me see if I can say this more clearly. For sake of argument, say the static friction of our ten-foot see-saw requires 50 foot-pounds to get moving. Put 4.9 pounds more weight on the opposite end than what the pisser weighs so we have a net torque of 49 foot-pounds - the see-saw doesn’t move. The pisser releases a pound of urine. Now there is a net torque of 59 foot-pounds and the see-saw moves.
Somewhere in the back of my mind I knew that 1 fluid ounce of water weighs 1 avoirdupois ounce, but I was much more acutely aware that 1 cc of water weighs one gram. So my immediate impulse was to come up with an SI quantity of water, then an SI mass, and convert back to avdp. And whaddya know, it was suspiciously close to a pound of water; I just wasn’t suspicious enough.
I’d say that’s pretty much the only design feature of the system, and as is typical for such a cobbled-together unit, we even got it wrong. A (US) pint of water weighs 16.69 ounces, more than two thirds of an ounce more than the design spec.
Maybe if you added a good crap the see saw would respond. My experiments show that a crap eliminates .8 to 1.5 pounds. I weighed in when I was in a weigh loss program. A good crap and a pee before weighing was worth 1.5 to 2 pounds on a very sensitive scale.
One thing to consider with this particular picture (hopefully I didn’t skim over someone else making the same point) is that the fellow in question is not done peeing yet. He clearly has a good stream still going in the After photo. So if this were a carefully balanced situation it will have to be closer than just full vs empty bladder.
