Required change in pressure to change volume

AI Thread Summary
To compress the volume of an iron block by 0.10%, a change in pressure (ΔP) can be calculated using the bulk modulus of iron, which is 9 x 10^10 N/m². The formula ΔP = B(ΔV/V) indicates that ΔV/V is 0.001 for a 0.10% change. The correct pressure needed is therefore 9 x 10^7 N/m². The discussion highlights a common mistake in interpreting the percentage change, emphasizing the importance of careful calculations. Overall, accurate application of the bulk modulus is crucial for determining the required pressure.
ryan.howie
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Homework Statement



How much pressure is needed to compress the volume of an iron block by 0.10%?

Homework Equations



the bulk modulus of iron= 9*10^10
delta_P= B*Vo/delta_V

The Attempt at a Solution


I have tried using random volume for example 1 and 0.01, and 2 and 0.02 but i feel i am way off.
 
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ryan.howie said:

Homework Statement



How much pressure is needed to compress the volume of an iron block by 0.10%?

Homework Equations



the bulk modulus of iron= 9*10^10
delta_P= B*Vo/delta_V

The Attempt at a Solution


I have tried using random volume for example 1 and 0.01, and 2 and 0.02 but i feel i am way off.

Welcome to PF.

Why do you feel you are way off?

Note though that B = ΔP/(ΔV/V)

http://hyperphysics.phy-astr.gsu.edu/hbase/permot3.html#c1

They give you already that ΔV/V = .1%
 
Thanks for the welcome and quick reply,

so ΔP=B(ΔV/V)
and B=9*10^10
and as you said ΔV/V=1%
so the change in pressure should be 1% of B which 9*10^8 N/m^2
but this is one of my previous answers and is wrong.
 
ryan.howie said:
Thanks for the welcome and quick reply,

so ΔP=B(ΔV/V)
and B=9*10^10
and as you said ΔV/V=1%
so the change in pressure should be 1% of B which 9*10^8 N/m^2
but this is one of my previous answers and is wrong.

Reread the problem statement, and my statement again.
How much pressure is needed to compress the volume of an iron block by 0.10%?
They give you already that ΔV/V = .1%
 
Sorry that was a stupid mistake. The pressure needed should be 9*10^7. thanks you for your help:smile:
 
ryan.howie said:
Sorry that was a stupid mistake. The pressure needed should be 9*10^7. thanks you for your help:smile:

Let's be more generous and call it careless.

As they say:

Careless happens.
 
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