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/sci/ - Science & Math

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2493545 No.2493545 [Reply] [Original]

If I peed off a roof 20 feet in the air, how cold would the temperature need to be for my piss to freeze before it hit the ground?

Assume my dick is 2 feet off the roof

>> No.2493559
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2493559

>>2493545
>Assume my dick is 2 feet off the roof

>> No.2493563

pretty cold

>> No.2493571

Probably cold enough that your exposed wang would get frostbite.

>> No.2493578

>>2493545
start at 35 degrees C and you want to go to 0 degrees in roughly 1.2 seconds....

>> No.2493587

>>2493559 OP here
by 2 ft off the roof, I meant 2 ft. above it.

Now that i look at my legs, they look longer than 2ft, but i only want an estimate.

>> No.2493596

>>2493578
plus the heat of fusion

>> No.2493598

>using arcane units for scientific calculations

>> No.2493599

Use newton's law of cooling. You'll have to figure out what the constant in the equation is in the case of a stream of pee, and I don't know how you'd do that.

>> No.2493602

7/10, good job OP
10/10 if a valid answer is found

Don't wee have to account for the temperature change to 0C as well time to lose the latent heat of the solid-liquid transition? Chem was a long time ago.

>> No.2493618
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2493618

>>2493602
I c wat u did thar

>> No.2493646

You also have to consider that temperature changes as you move through different air masses. This is why precipitation that starts out as snow can melt as it hits warmer air, then re-freeze when it hits cooler air, eventually landing as sleet.

So depending on the height of the building and the air around the building you might need a variety of different temperatures to achieve the exact form you want on the ground.

>> No.2494168

>>2493646 OP here
The height of the building is 20 feet. Assume uniform temperature.

>> No.2494176
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2494176

>>2493602
>Don't wee have to
>wee

>> No.2494186

/sci/ can't do actual science.

>> No.2494196

>>2494186
dude this is an impossibly hard question theoretically. First of all things flowing turbulently tend to not freeze despite being at freezing temperatures. And if we ignore the turbulent flow then it wouldn't cool down as fast because heat transfers quicker through turbulent flow.

I say you just test it experimentally.

>> No.2494236

>>2494196
I was thinking of using a cylindrical section of pee and using stefan boltzman law in integral form to get the result.

>> No.2494274

Problem is OP, once your wang is out in the cold it will shrink and you will have to add the distance of the shrinking over time.

>> No.2494312

I can answer this is you tell me the angle of the stream and the velocity of your piss.

>> No.2494340

>>2494312
Also how much does 1 ml of piss weigh

>> No.2494356
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2494356

>not using SI measurements

>> No.2494378

>>2493545
I live in Canada, I'll try it next January when it's -30°C

>> No.2494381

>>2494356

That's why I'm asking
OP are you even there or will I have to fudge the numbers?

>> No.2494401

is op arching or shooting straight down?

what is the exit speed?

>> No.2494402

>>2494340
mostly water so 1 gram.

>> No.2494460

>>2494401
Let's assume best possible airtime.
Does anyone know the velocity of piss leaving the urethra?

>> No.2494483

>>2494460

We still need the angle of exit though :(

>> No.2494531

>>2494483
I'll assume 45 degrees will give best airtime

>>2494460
mine varies depending upon back pressure.

>> No.2494548

22 feet = 6.7 meters
d=1/2a*t^2
1.368 seconds squared
1.17 seconds until it hits the ground
body temp: 300K
freezing temp of water: 273.15K
you have two equations (exponential decay for the two points)
T=(300-f)e^-kt+f
T(0)=300=(300-f)*1+f=300
T(1.17)=273.15=(300-f)*e^-k1.17+f
two unknowns (f and k) and only one equation. you can't solve it.
however, you can guess at that coefficient. (k)
I'll let you do this.

>> No.2494573

>>2494531

Ok so so far we have:

dy= 6.7056 m
Theta = N45S
v = ???
Need to find T or t

Need v

>> No.2494576

>>2494548

Aw you ninja :(

>> No.2494644

>>2494483
I'm getting a time of... [(2V/g)+SQRT(2(6.6-V)/g)]
Where V equals the initial velocity of the urine, g is 9.81m/s^2, and 6.6 is the hight of the building+legs, in meters.
Assuming we start with a body temp of 36.6 degrees Celsius, and that urine freezes at 0 degrees Celsius....
Fuck, I dropped out of the physics program because I didn't want to have to deal with this Laplacian operator shit.

>> No.2495368

OP here

wtf do you guys seriously pee at a 45 degree angle?

I haven't used a protractor, but i feel like my dick is usually at a -45 degree angle (0 being parallel to the earth)

You guys can seriously put anything you want into the variables, it's a theoretical question so i don't really care if the equation is only for "X degrees"

>> No.2495387

>>2494548
undergraduate failure detected.

>> No.2495504

>>2495368
we were assuming best possible airtime.

>> No.2495639

>>2495504
OP here

I guess you could use 45 degrees, but I know I would never pee at that angle. I think 15 could be practical, or 20 or some shit like that.

>> No.2496122

bamp