How Can the Weight of a Human Head be Measured?

[I_am_learning]

Just in the middle of random discussion with my friend, we wondered how could the weight of a human head (the portion above neck) be measured?
Of-course without doing nasty things. (eg. chopping. )

 

[lisab]

To what accuracy?

 

[Jimmy Snyder]

I'm afraid I can't help you. I always chop.

 

[rollcast]

http://www.guardian.co.uk/notesandqueries/query/0,,-1244,00.html

That describes a few methods for approximating it although I'm not sure of the accuracy of some methods

According to the Department of Anatomy & Histology, University of Sydney, an adult human cadaver head cut off at vertebra C3, with no hair, weighs between 4.5 and 5 kg (between 9.9 and 10.23 pounds).

Or you could lie ona table and then rest your unsupported head on a set of scales just over the edge of the table

 

[I_am_learning]

To what accuracy?

Resolution: < 0.1Kg
Permissible Error: < 0.1 Kg
But you can't assume that the head you are measuring is an ordinary type of head. It could have a ~1kg of bullets stuck on somewhere and the person might still be living. Point is, you neither know its tentative weight nor do you know its mass distribution.

 

[jedishrfu]

Resolution: < 0.1Kg
Permissible Error: < 0.1 Kg
But you can't assume that the head you are measuring is an ordinary type of head. It could have a ~1kg of bullets stuck on somewhere and the person might still be living. Point is, you neither know its tentative weight nor do you know its mass distribution.

it seems a 1kg of bullets is pretty nasty.

Note to Jimmy: buy life insurance and avoid chopping bullets.

 

[Danger]

I agree with Jimmy on this one; if I can't chop, I'm not interested.

 

[Jimmy Snyder]

Reminds me of my beloved cousin Alphonse C. Snyder. According to the police report, he shot himself in the back of the head 27 times with a rifle from close range. When I chopped his head off to weigh it, the axe hit several bullets. It was so dull I had to replace it. You can well imagine my grief at the loss.

 

[cng99]

Well, the mass can be easily measured by balancing torque once you locate the center of mass of the head.
The trouble is thus the center of mass.

 

[Danger]

It was so dull I had to replace it.

Well duh, you silly ***. Everyone knows that you use a titanium axe for gunshot victims.

 

[I_am_learning]

Well, the mass can be easily measured by balancing torque once you locate the center of mass of the head.
The trouble is thus the center of mass.

Can you elaborate please?

 

[daveb]

I'm sure this has the correct answer https://www.youtube.com/watch?v=0Jkm6aYYdB8

 

[Ken Natton]

They covered this on QI. Basically, the technique is to stick your head in a bucket of water and measure the volume displaced. The underlying assumption is that the average density of the head balances out pretty close to that of water, an assumption, they assured us, that is reasonably accurate.

 

[Danger]

The underlying assumption is that the average density of the head balances out pretty close to that of water, an assumption, they assured us, that is reasonably accurate.

So you're pretty much guaranteed of success if your subject is hydrocephalus.

 

[Jimmy]

Hmm, so the OP should go soak his head? Not as good as chopping but it'll do.

 

[Hepth]

I don't think that's accurate Ken. Thats just volume of head x density of water.

I think you can do it by weighing yourself in a pool once with your whole body in, and once with your head above water. Also measure the displacement to get the volumes of your body and head. There are enough knowns to solve your head weight out of water.

 

[Ken Natton]

Okay, well, what they pointed out on QI is that the way to do it accurately is to use an MRI scanner. However, if you don't have access to such a thing, the head in the backet technique is a pretty good approximation. So they said anyway. Can't say I've ever tried it myself.

 

[Danger]

If you're not allowed to cut off the head and weigh it, there is an equally accurate and more socially acceptable method. Cut the body off instead, then just weigh what's left over.

 

[I_am_learning]

I don't think that's accurate Ken. Thats just volume of head x density of water.

I think you can do it by weighing yourself in a pool once with your whole body in, and once with your head above water. Also measure the displacement to get the volumes of your body and head. There are enough knowns to solve your head weight out of water.

In the text below and in all subsequent replies, 'Torso' refers to Whole body minus head.

Ok. We have volume of Torso and volume of head.
Now, as you suggested to measure,

1. Weight of whole_body inside water = Actual Body weight - weight of displaced water.
   We don't actually need to measure it, i.e. we won't get any extra information by measuring it , because weight of displaced water = volume of body * density of water
2. Weight of only Torso inside water= Actual Body weight - weight of displaced water by Torso
   Similar case as above.

So, we don't have enough knowns, but instead to many redundant knowns.

 

[Jimmy Snyder]

Why don't you just soak your head?