physics help please...
posted by julie on .
A light spring of constant k = 170 N/m rests vertically on the bottom of a large beaker of water. A 5.70 kg block of wood (density = 650 kg/m3) is connected to the spring and the massspring system is allowed to come to static equilibrium. What is the elongation, ÄL, of the spring?
im using the equation of the spring constant... F=kx F being Bweight. and i keep coming up with the wrong answer. please help me!!!

volume of wood = (5.7/650) m^3
difference in density = 1000650 = 350 kg/m^3
net force up = 350 (5.7/650)(9.81) = 30.1 N
F = k x
30.1 = 170 x
x = 30.1/170 = .177 meter 
why is the difference in density 350? where does the 1000 come from?

water density = 1,000 kg/m^3
close enough :) 
the 1000 kg/m^3 is the density of water.

I used the difference in wood and water density to get the net buoyancy.