Big C

This may sound a bit strange, but here goes:

Short of cutting the thing off,
how would I tell the weight of say my head, or right arm to a good degree of accuracy (say +/- 3%).
I suppose what I am looking for is a method of dioing this without using the bathroom scales. I'm sure there must be a weigh.
Didn't Archemedes have a way around this type of thing?

Let the wisecracking begin.

C

corvid

If you displace water with your noggin then weigh the water I think that would be the only way - just a guess..

Freak

You need a human size version of a eureka can

Basically Brim a bucket full of water.
Dunk your head/arm in it and you need to measure how much water gets displaced and pushed out of the bucket(maybe put the bucket in the bath so its collected and you can measure it)
You can then work out from this amount and the original amount in the bucket how mcuh it weighs... sounds incredibly daft- and its probably wrong, but hey....

(Very)Vaguely remembered from school physics lessons.....

Geezer

What you are talking about is displacement, not weight. A 30cm diameter ball of polystyrene will displace the same amount of water as a 30cm diameter ball of gold, so it's volume not weight. The density of the water will not necessarily be the same as what is displacing it, so it is no a reliable method.

I don't know of a way to do this however, I'm sure someone on here will though.

Geezer

MartinM

So dunk a blown up balloon in the bucket...
Weight of water displaced = lots
Weight of balloon = bu$$er all

hmmmm...."Houston, we have a problem"

Volumes are equal however, so doing hard sums with relative density of water, air and rubber would give an answer - anyone know the relative density of a head

Freak

MartinM

There's a few ideas here:
http://www.halfbakery.com/idea/Weigh...r_20own_20head

I like the one along teh lines of

"Lay your head on a bathroom scale, and then look up really quick to see what it reads. It doesn't work, but its fun to watch someone doing it"

RichWalk

Go on a forensics based site they should advise average weights per body part per size/weight of males/females etc, then work on their models.

David Lock

Local mortuary?

Big C

nice so far, think I have had a think at all of those. The most obvious to me was the sitting in a bath/head in bucket option, but the arguments already outlined disprove that method. There must be a weigh however to link displacement via the relative mass to give a pretty accurate answer. I'm sure ballistics experts could provide a view on the density of the human head when calculating projectile velocity through that medium etc..)

Interrogating forensic models will give me ball park, but i am looking for a relative degree of accuracy for a specific individuals anatomy (with the usual variables as issues - being 'big boned' etc
These variables area big enough factor to rule out this method.
The half bakery website seems to be addressing the issues but hasn't got there quite yet. Some good ideas though using MRI etc...

Any more for any more?

cheers,
C

AvalancheS8

The law of physics being incorrectly applied in these ideas is " a floating body will displace it's own weight of water" so it will only work with things that float, or as a way of finding the volume of something if you know the density of. Your head might, or might not float on it's own but it would be nigh on impossible get it to float with no influence from the rest of your body while it's still attached. That said, the average human body only just floats anyway (some float well, others not at all - I don't, or at least not in fresh water), so I wouldn't be surprised if the density of a head is pretty cloase to that of water, so the "stick your head in a bucket" trick might work as a start. You don't need to catch and measure the displaced water, just start with it full to the brim - plunge body part - remove body part - carefully measure how much water you need to add to fill it back up. Or better yet weigh the full bucket and then weigh it again after displacing some with your head.

STi wanna Subaru

iTrader: (1)

mate, just accept you have a fat head and get over it!


sorry, can't offer anything constructive

Big C

LOL

Geezer

But does 'pretty close' come close enough for his needs? I doubt it. Any given volume of water will not necessarily weigh the same as another anyway, due to differences in temperature. 1m cubed of ice doesn't weigh the same as 1m cubed of water! Weight is determined by gravity, not volume or density.

Geezer

Rathy

Assuming this isn't a wind up, then you can use Archimedes principle, which is roughly: an object is buoyed up with a force equal to the weight of the liquid it displaces.

Probably best to read these intructions through to the end to avoid drowning yourself. Oh and if you do that's not my fault

Get a bucket and fill with water.
Weigh bucket
Place head into bucket, displacing water up to your neck.
Take head out of bucket
Re-weigh bucket
Substitute second weight from first weight and you have the weight of your head.

This method works for all limbs, limited only by the size of the bucket you can obtain and your, err, imagination

Cheers,

Rathy, with too much time on my hands.

Brendan Hughes

Not enough time to read the thread properly though. You're mixing weight with volume.

Chrisgr31

Ok to weigh your head, get on scales and weigh your whole body.

Now fill your bath to the brim with water, climb in and put your whole body underwater. Stayunderwater until all the excess water has flowed over the edges and'or disappeared down the overflow.

Climb out the bath, and empty the remaining water with a measuring jug.

You now know how much water you displaced. Divide your bodyweight by the water displaced to give you your body density.

Now you can stuff your head in a bucket of water, measure the volume of water lost and calculate the weight from that by using the density arrived at above.

Midlife......

iTrader: (2)

Nahh!

Need to use the equation Force=Mass x Accelleration.

Apply a known force to head , a handy sized baseball bat will do and measure acccelleration of head with accellerometer and hey presto.

I suggest you only do this once and bear in mind destructive testing of humans may be ilegal.

Midlife.....

IWatkins

Man, this is too easy......

Saw your own head off and put it on some weighing scales.

clarky1982*

why the fck do you want to weigh your head anyway

matt85

LMAO @ this thread!!

Tiggs

did the people who suggested the water/displacement idea have their adult helpers log them on a pc?

my 3 year old isnt that thick!

LG John

Look mate I'll save you a lot of time and effort and tell you right now.........you do NOT have a 2lb ****

Atom290

Ive just done it!

We aren't able to measure the weight of a head directly but we can measure its volume and guess its density on the assumption that the brain, like the rest of the body, is mostly water and we know the density of water at 0 °C.

To measure the volume of the head, virtually bald, I lowered my head into a bucket of water filled to the brim. The water has to be near to 0 °C, so it was bloody cold, I lowered it vertically and crown downwards until the water reached the base of my chin. The water that spilled over the sides of the bucket was collected in a larger bowl in which the bucket was standing in and its volume measured. I repeated this five times and the average volume of water displaced was 4.25 litres, giving an estimate of the weight of a human head at 4.25 kilograms

Atom290

has anyone got a towel?

+Doc+

An adult human cadaver head cut off around vertebra C3, with no hair, weighs somewhere between 4.5 and 5 kg, constituting around 8% of the whole body mass.

Google is handy sometimes

Clett

I'd agree with Atom on this one. The density of various human bits is more or less 1 (kg per litre). Don't worry too much about the temperature of the water though, it's densest at 4oC, and not much different at other temperatures you're likely to stick your head into. Bear in mind also that unless you expel all the air in your cavities, these will count as mass too when doing it by volume. I would suggest some caution in this matter.

Atom290

Did the whole experiment in a vacuum, oh and I breathed out until I was purple!!

GU5

Just make it up, without cutting off the head being weighed nobody will know