# Physics (maybe it's just math)

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A sphere of copper is subjected to 89.7 MPa of pressure. The bulk modulus is 130 GPa. a) By what fraction does the volume of the sphere change? b) By what fraction does the radius of the sphere change?

for a) I have dV/V = 0.00069 - this is correct.

for b) the area I have 4/3 x pi x r^3.

I did the following:

Try 1 - 0.00069 = 4/3 x pi x dr^3 - wrong

Try 2 - then I took the cube root of 0.00069 and got 0.088 - wrong.

Try 3 - I used the same factor of 0.00069 since the radius is all that is changing in the equation - wrong.

Try 4 - I tried factoring dr = rfinal - rinitial and I'm left with something I don't know how to deal with.

HELP! Is it 4 and I need to use some algebra technique I can't remember how to do???

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