# Easy question for you guys

• AshyLarry
In summary, the conversation discusses a physics problem related to pressure, volume, and a constant (k). The equation y=k/x is mentioned, and it is explained that k can be solved for by multiplying by x on both sides. It is also mentioned that the ideal gas approximation can be used in simple problems, and that more information is needed to solve the given problem.

#### AshyLarry

Need help for a friend...Easy

I took physics last year at HS. and my buddy is asking me for help and I can't remember any of this. Here is what I know

What is the value for volume for a pressure of 500 torr?
y= volume 160
k= constant
x= pressure 500

y=k/x

what is k the constant ?

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Are you given that the volume is 160 (units?) and need k? In that case solve for k by multiplying by x on both sides to get k=yx. Above the equations you ask what the volume is, which confuses me a little. If you do not know k, you can't find the volume, since k will depend on the temperature.

Are you talking about PV=nRT? (P=pressure, V=volume, n=# of moles, R=universal gas constant, T=temp.)

So the idea is there will be some function relating pressure, volume, temperature (absolute), and number of entities. The ideal gas approximation is often used in simple problems and asserts that
PV/nT=R
where
P=pressure
V=volume
n=number of entities
T=temperature (absolute)
this also means that
P1V1/n1T1=P2V2/n2T2
so one variable can be found if all others are known, or known to not change.