help physics

[teznela]

who can get there head around this please it is an example I have worked on and probably got totally wrong

You take a gas volumn of 2 litres in a flexible container from the surface to a depth of 17m in sea water. WHat will the new voloumn be, and what willl the density be compared to the surface

any help much needed

tez

 

[vondo]

who can get there head around this please it is an example I have worked on and probably got totally wrong

You take a gas volumn of 2 litres in a flexible container from the surface to a depth of 17m in sea water. WHat will the new voloumn be, and what willl the density be compared to the surface

any help much needed

tez

Ok, start with PV = nRT

R is constant, since it is sealed, n is constant. T is assumed to be constant (basically true). So on both the surface and at 17m P*V is the same number. On the surface, P=1 atm. down 17m, P = 2.7 atm. The rest is arithmetic.

 

[richarddean]

??????

 

[bperrybap]

Boyle's law.
P1*V1 = P2*V2
Isn't this covered in OW class?
Here is some good reading on the gas laws:
Gass Laws

--- bill

 

[SparticleBrane]

Ok, start with PV = nRT

R is constant, since it is sealed, n is constant. T is assumed to be constant (basically true). So on both the surface and at 17m P*V is the same number. On the surface, P=1 atm. down 17m, P = 2.7 atm. The rest is arithmetic.

There is absolutely no reason for you to use the Ideal Gas Law to solve this problem. This is a Boyle's Law problem.

 

[vondo]

Where do you think Boyle's Law comes from? If you understand the ideal gas law, Boyle's law follows very easily from it. Memorizing Boyle's law is like the people who memorize three different Ohm's laws: V=IR, R=V/I, and I=V/R. (Yes, some people are taught this!)

 

[dumpsterDiver]

Where do you think Boyle's Law comes from? If you understand the ideal gas law, Boyle's law follows very easily from it. Memorizing Boyle's law is like the people who memorize three different Ohm's laws: V=IR, R=V/I, and I=V/R. (Yes, some people are taught this!)

Exactly! just learn one law and then figure the rest out from there. I always had problems memorizing the NAMES of the laws

 

[RedCash02]

There is absolutely no reason for you to use the Ideal Gas Law to solve this problem. This is a Boyle's Law problem.

Maybe to illustrate the fact that the only law you need to know for problems of this nature is the ideal gas law. Boyle's Law is just a special case of it when T and n are held constant. Also, the problem statment left out whether or not T could be assumed constant.

It's kind of like memorizing a bunch of equations for volumes of solids or knowing the calculus to derive any of them. The former may be faster, but doesn't give a fundamental understanding.

 

[RedCash02]

Haha beat me to it. I shouldn't have got distracted. I may be stuck in an engineering mentality though and maybe some people can't make the required transformation when they see P*V=n*R*T and only know P and V in a test setting. It might be better for them to memorize multiple equations.

 

[Thalassamania]

I have to admit I tend to use the ideal gas law too, it does everything and you only have to remember one stupid name.