Posted by **julie** on Monday, December 20, 2010 at 7:05pm.

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 mass-spring 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 B-weight. and i keep coming up with the wrong answer. please help me!!!

- physics help please... -
**Damon**, Monday, December 20, 2010 at 7:15pm
volume of wood = (5.7/650) m^3

difference in density = 1000-650 = 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

- physics help please... -
**julie**, Monday, December 20, 2010 at 7:23pm
why is the difference in density 350? where does the 1000 come from?

- physics help please... -
**Damon**, Monday, December 20, 2010 at 7:28pm
water density = 1,000 kg/m^3

close enough :)

- physics help please... -
**bobpursley**, Monday, December 20, 2010 at 7:28pm
the 1000 kg/m^3 is the density of water.

- physics help please... -
**Damon**, Monday, December 20, 2010 at 7:28pm
I used the difference in wood and water density to get the net buoyancy.

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