measure the psi of a stream of urine?


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the other night we were joking around and someone put up the question of how one would measure the psi of a stream of urine exiting the body. im sure it can be measure... only question is... how? does anyone know? i know it sounds weird, but i want to know. thanks.

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The normal bladder resting pressures vary between 8 and 40cm of water (ie the pressure exerted at the bottom of a column of water 40cm high)

Hmm...thats the bladder at rest. So how much PSI is at the bottom of a 40cm coloumn of water? Well, its the weight of 40cm of water exerted on one square inch. 1 cubic centimeter of water weighs 1 gram, so thats 40 grams. How many pounds? About .089 pounds. Not much so far.
Many women void simply by relaxing the urethral sphincter with no associated rise in detrusor muscle pressure

Hmm...squeezing it out increases the pressure.

So. When the flow is restricted through a smaller opening, the pressure will rise. Thats why if you take the end off your garden hose there isn't much pressure at all, it just runs out. But if you put your thumb over it and restrict the flow, the pressure will spike.

So, if you take the normal resting bladder pressure, calculate the passageway through which the volume of urine must flow and the increase in pressure due to the detrusor muscle, you will know the pressure at which urine exits the body.

I imagine some scientist somewhere has done the math...I think I am going to go do something easy, my brain is sweating already. If I had to guess I'd say its somewhere around 2PSI. Depending on if you are trying to give yourself a hernia or not...

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Any easy way to measure it (for a man atleast) would be to lay on the ground - pee straight up. Measure the height of the stream - then do the math.

Simple! ;)

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Hmm...thats the bladder at rest.  So how much PSI is at the bottom of a 40cm coloumn of water?  Well, its the weight of 40cm of water exerted on one square inch.  1 cubic centimeter of water weighs 1 gram, so thats 40 grams.  How many pounds?  About .089 pounds.  Not much so far.

He wanted pressure, not force. 40cm^3 of water does not WEIGH 40 grams, it has a MASS of 40 grams. You want pressure which is measured in Pascals (N/m^2). So, the pressure under 40cm of water is:

pressure = (density of water) * (gravity) * (height of water)

= (1000kg/m^3) * (9.81 m/s^2) * (.40m)

= 3924 Pa

Converted to PSI, that would be 0.56913 psi.

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Any easy way to measure it (for a man atleast) would be to lay on the ground - pee straight up. Measure the height of the stream - then do the math.

Simple! ;)

That would give the force of the pee coming out, not it's pressure. To get the pressure, you'd have to divide the force by the area of the hole.

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That would give the force of the pee coming out, not it's pressure. To get the pressure, you'd have to divide the force by the area of the hole.

Like I said - do the math. But you need a way to measure the force of the stream. So how high it goes against gravity would be the easiest method.

So unless you want to stick a pressure gauge you know where ;)

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This thread is about as intelligent as the one Ryan posted about flatulance. Grow up people. This is not pre-school, although sometimes it sure as hell feels like it. (N)

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