I've been given that there is a spring holding a $.25kg$ mass where $k=10N/m$ and is held at $40cm$ and then let go. I've found that the max velocity is $2.53m/s$ and that when the spring is at $20cm$ the velocity is $2.19m/s$
What I'm having a hard time wrapping my head around is finding the position when the kinetic energy and potential energy are equal.
I keep trying to arrange it like so but end up with two unknowns
$.5(10N/m)(\Delta x)^2 = .5(.25kg)v^2$