Help with oscillating spring and energy

[dorkymichelle]

Homework Statement

A 0.50-kg block attached to an ideal spring with a spring constant of 80 N/m oscillates on a horizontal frictionless surface. The total mechanical energy is 0.12 J. The greatest speed of the block is:

Homework Equations

E mech = 1/2kx^2+ 1/2mv^2

The Attempt at a Solution

Mechanical energy = Spring potential energy + kinetic energy

E mech = 1/2kx^2+ 1/2mv^2
0.12J=1/2(80)^2+1/2(50)V^2
but I have two unknowns, v and x...

 

[the_kool_guy]

for greatest velocity... equate x=0 ..
the greatest velocity in on mean position where x=0
...
and total energy of system is conserved at any tym