Homework Help: Hydrolic Pressure and Bulk Modulus

1. Sep 3, 2008

vMaster0fPuppet

1. The problem statement, all variables and given/known data

A solid copper cube has an edge length of 87.0 cm. How much pressure must be applied to the cube to reduce the edge length to 85.7 cm? The bulk modulus of copper is 1.4 multiplied by 1011 N/m2.

2. Relevant equations

Vcube= s^3

F/A=(B x deltaV)/V
p=F/A
p=(B x deltaV)/V

3. The attempt at a solution

V= (.870m)^3= .659m^3
Vn= (.857m)^3= .629m^3
deltaV= V-Vn= .03m^3

p=(1.4e^10N/m^2)x(.03m^3)/(.659m^3)= 6.37e^9N/m^2

This is apparently not the answer???

2. Sep 3, 2008

LowlyPion

Is that 1.4 x 1010 Pa or 1.4 x 1011 Pa.
I think think it is 1.4 x 1011 Pa for copper as you originally gave in the problem.

3. Sep 3, 2008

vMaster0fPuppet

Its 10^11, and I did the calculations with 10^11.

Thanks anyway, I actually figured the problem out. When I used .870^3-.857^3 for deltaV the calculations worked just fine. I didn't realize that making the calculation easier by breaking it up would cause such a problem if I used the correct number of significant figures.

4. Sep 3, 2008

LowlyPion

OK then rightio. I didn't see a problem with your method.