I don’t understand why there aren’t more people in the Western world using bidets or bum guns.
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So you’re saying a prolapsed anus would, in fact, help?
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I missed all this the first round lol
Isn’t all this disproven by the fact that the water you pour out is still moving with you and therefore it keeps the momentum it has when it was in the bottle.
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In this case you aren’t throwing the water, simply holding it ahead of you while accelerating.
actually, throwing the water battle behind you would increase acceleration, newton’s third law
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The other discussion involves descending a hill, then throwing the water backwards to a standstill. Careful analysis reveals the rider harvests the work/effort from the throw (which would also be the case pushing off the ground), but additionally the rider harvests the GPE (gravitational potential energy) the bottle had before the descent.
and the water floats in the air behind because it’s gravitational potential energy has been transferred to the rider?
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It would be based on the difference in height from holding the bottle at the top of the hill versus holding it at the bottom of the hill.
oh. i thought we were talking about the thowing the water behind you.
holding it yah, makes sense. DH skaters have experimented with weights a fair bit.
Think of it this way, you throw at top of the hill (from a standstill - same effort), some of the effort gets wasted accelerating the bottle backwards (you still get some energy, but less than pushing off the ground).
You throw at the bottom of the hill (same effort), the bottle is momentarily at rest relative to the ground as it leaves your hand. In this case you got all the throw effort, plus the energy from the height difference.
no.
all you get is the newtons third law bit.
The surprising result arises from the Oberth Effect which obeys Newton’s 3rd law.
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an increase in energy is not the same as an increase in acceleration.
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The easiest way to visualize it is the final velocity of the rider will be greater if they descend the hill then throw the bottle rather than throwing the bottle 1st and then descending the hill.
The way to visualize it is… the acceleration from throwing the water bottle will be the same top and bottom of the hill. but the change in kinetic energy will be higher when going faster since kinetic energy goes up with the square of the velocity.
but you are correct by carrying a weight down the hill you will have gained extra acceleration (converting GPE to velocity) the entire way down the hill. and therefore final velocity will be higher from that effect alone.
If you throw at the top, you end up with a water bottle with kinetic energy at the top of a hill.
If you throw at the bottom such that the water bottle is momentarily at rest to the ground as it leaves your hand, you have a bottle with 0 kinetic energy and lowered height.
If we carefully compare the final energy state of both thrown bottles, the 2nd bottle has less- less kinetic energy and less gravitational potential energy.
Indeed it would take energy to get it back to the top of the hill, and more energy still to give it the kinetic energy of the 1st example. This “missing energy” from the final state of the thrown bottle in the 2nd example goes to the rider.
what’s the difference in velocity between these two:
a. carry water bottle down hill. throw at bottom.
b. throw one water bottle at top of hill, carry equal mass water bottle down the hill.
i mean roughly you’ve just agreed with me. the increase in final velocity is due to carrying a mass down the hill.