# Homework Help: Bulk modulus and density

1. Jul 8, 2010

### mandy9008

1. The problem statement, all variables and given/known data
The deepest point in the ocean is in the Mariana Trench, about 11 km deep. The pressure at that point is huge, about 1.13 x108 N/m2.
(a) The deepest point in the ocean is in the Mariana Trench, about 11 km deep. The pressure at that point is huge, about 1.13 x108 N/m2.
(b) The density of water at the surface is 1.03 x103 kg/m3. Find its density at the bottom.

2. Relevant equations
P=B(ΔV/V)

3. The attempt at a solution
a. 1.13 x108 N/m2 = -(2.15 x109 Pa)(ΔV/(1.00 m3))
ΔV = -0.053 m3
b. Since water is not compressible, shouldn't the density be the same at the bottom of the ocean as the top?

2. Jul 8, 2010

### Tusike

Well, everything is compressible, only the force required to compress it is different for each material. I don't know what your a. question was, since it seems you copied it wrong, but I see you calculated some sort of deltaV. If the volume changed, shouldn't the density have also changed?

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

3. Jul 8, 2010

### mandy9008

yes, i did copy part a wrong. the question for part a was: (a) Calculate the change in volume of 1.00 m3 of water carried from the surface to the bottom of the Pacific.
so, if the density is different, how do i determine the change?

4. Jul 9, 2010

### Tusike

Well I'm not sure, but you should be able to calculate the weight of 1m3 water (don't know the density of sea-water...), and after you carried it down, the mass is still the same, so because m = qV, where q is density, you could say q1*V1 = q2*V2, and only q2 is unknown.