So technically, you are correct. The force is the water pressure provided by the piss being pulled down by gravity. Practically speaking, this force is negligible because all you’re doing is allowing the piss to fall, not forcing it downwards.
Basically, imagine you’re holding an incredibly heavy rock that does not have a gravitational field or air resistance. If you drop the rock, gravity will pull it down, but regardless you will not go up unless you apply force and throw it down.
That bladder has muscles around it that tighten once the sphincter muscles at the base of your bladder relax to let urine through the urethra. So you can and do apply more pressure than just gravity. Just not nearly as much as OP’s idea needs.
So technically, you are correct. The force is the water pressure provided by the piss being pulled down by gravity. Practically speaking, this force is negligible because all you’re doing is allowing the piss to fall, not forcing it downwards.
Basically, imagine you’re holding an incredibly heavy rock that does not have a gravitational field or air resistance. If you drop the rock, gravity will pull it down, but regardless you will not go up unless you apply force and throw it down.
That bladder has muscles around it that tighten once the sphincter muscles at the base of your bladder relax to let urine through the urethra. So you can and do apply more pressure than just gravity. Just not nearly as much as OP’s idea needs.