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-   -   Houston, we have a problem or two... (https://www.goldwingfacts.com/forums/4-miscellaneous-forum/665821-houston-we-have-problem-two.html)

Peter Goldwing 12-12-2018 07:10 PM

Houston, we have a problem or two...
 
I always wondered what the correct answer for these problems are:
Suppose you have this glass room entirely sealed from outside. It weighs 300 lb (just like my frigging doors) Inside we have a model helicopter on the floor. The air inside + the glass room + the helicopter weighs 320Lb.

Will the weight of this sealed room change once the helicopter hovers above the floor?
Id say no, but no scientific proof.

Second problem: we have the same room with something small combustibile inside . We remotely set this thing on fire and there is enough oxygen/air for it to burn completely.
Will the weight of the room change?

tamathumper 12-12-2018 07:17 PM

Here's my guess(es):

In the first instance, the mass of the combined objects does not change, but the measurable "weight" of the combined objects changes as the helicopter flies around and applies different amounts of downforce against the floor. At that point you're not measuring weight (alone) any more.

In the second instance the weight of the room will change, as all the mass that is converted into non-material forms of energy with mass escapes by radiation through the glass.

Peter Goldwing 12-12-2018 07:59 PM

Hmm. I really like your avatar.I love animals.

Regarding the second answer I'm not sure energy has mass, though I heard someone say that a wound up spring it heavier that a relaxed one.

Is a charged battery heavier than a discharged one? Dont know

BLUTHUNDR31 12-12-2018 10:05 PM

Scenario #1: While the helicopter is airborne, the room will be lighter by the same amount as the static weight of the helicopter. Once the helicopter lands, , , room weight will include the weight of the helicopter.


Scenario #2: The weight of the "small combustible mass" plus the weight of the detonator is included in the original "room weight". After the "burning" of the mass plus whatever amount of the detonator that burns will make the room lighter by however much the difference between original mass compared to burned mass plus the original weight of the detonator compared to the weight of the detonator AFTER detonation. Some mass will be lost, and so weight will be LOST.


**A 10 lb. log that is burned completely will NOT produce 10 lbs of ash

DaveO430 12-12-2018 10:12 PM

I don't know but I think tamathumper is wrong on the first and right on the second.
Einstein said mass = energy or something like that & he seemed to be pretty smart. And a charged battery should weigh more than a discharged one, the electrolite's specific gravity is more when it's charged.

Wes Scott 12-12-2018 11:33 PM

Quote:

Originally Posted by tamathumper (Post 5809485)
Here's my guess(es):

In the first instance, the mass of the combined objects does not change, but the measurable "weight" of the combined objects changes as the helicopter flies around and applies different amounts of downforce against the floor. At that point you're not measuring weight (alone) any more.

In the second instance the weight of the room will change, as all the mass that is converted into non-material forms of energy with mass escapes by radiation through the glass.

For the first instance, the original problem statement said the helicopter was hovering so the downforce applied by the helicopter will be equal to the static weight so the measured "weight" would be the same. The weight will fluctuate as the helicopter climbs (down force greater than static weight so "weight" will increase until the climb is stopped) or sinks (down force less than static weight so "weight" will decrease until the sink is stopped.

In the second instance the weight will not change. The energy that is released by combustion is stored in the chemical bonds of the material and/or the orbital energy of the electrons. When something burns the chemical bonds of the material and the oxidizer are changed (this includes the orbits of the electrons) but there is no mass converted into energy. (Mass into energy requires a nuclear reaction.) The radiation through the window allows the interior to cool but will not transfer any mass.

Wes Scott 12-12-2018 11:39 PM

Quote:

Originally Posted by DaveO430 (Post 5809537)
I don't know but I think tamathumper is wrong on the first and right on the second.
Einstein said mass = energy or something like that & he seemed to be pretty smart. And a charged battery should weigh more than a discharged one, the electrolite's specific gravity is more when it's charged.

A charged battery should weigh less than a discharged one since the charging process causes off gassing (some of the water in the acid is converted to hydrogen and oxygen). The specific gravity goes up because sulfate is being transferred from the plates in the battery back to the acid. So while the weight of the liquid goes up, the weight of the plates goes down. If you could charge a battery without creating any off gassing, the weight would remain the same.

DaveO430 12-13-2018 05:57 AM

Quote:

Originally Posted by Wes Scott (Post 5809547)
A charged battery should weigh less than a discharged one since the charging process causes off gassing (some of the water in the acid is converted to hydrogen and oxygen). The specific gravity goes up because sulfate is being transferred from the plates in the battery back to the acid. So while the weight of the liquid goes up, the weight of the plates goes down. If you could charge a battery without creating any off gassing, the weight would remain the same.

In a sealed battery?

tamathumper 12-13-2018 06:06 AM

I'm staying in a Holiday Inn Express next week, and I reserve the right to change my answers...

DenverWinger 12-13-2018 06:15 AM

In the combustion scenario some of the mass is converted to heat. Anybody figured out how to keep the heat inside, or weigh it?


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