[NewCandle] NR attempt at Fred's battery anti-lifter

[Horace Heffner]

On Aug 14, 2007, at 5:19 AM, Nick Reiter wrote:

>
> I think the mechanism by which cloth or paper would
> change weight with acquisition of H2O from the air
> would more likely be simply surface trapping rather
> than swelling and air displacement.

I think an inflated plastic bag should weigh the same as an empty  
one, assuming no increased air pressure. The bouyancy of the extra  
air matches its weight.

Bouyancy of displaced air is probably not a good explanation of  
Fred's weight change because the density of air is about 1.2 g/l or  
12 mg/cc. If Fred's scale were accurate to a mg it would be sensitive  
to a 0.1 cc change in volume, and effects of changes in volume might  
be seen, but it takes a whole liter's displacement to get a gram  
change in apparent weight, so that's out as an explanation I guess.   
I've made very inexpensive long beam knife edge fulcrum balances for  
EM thruster experiments that were very sensitive to incremental  
weight changes of much less than a mg, and thus the beam was also  
sensitive to expansion due to changes in temperature, which was not  
good. I had to go to a torsion pendulum to get good results.

Horace Heffner
http://www.mtaonline.net/~hheffner/