a mass is attached to a spring and released. it then oscillates in simple harmonic motion. what is the transformation of energy? i understand how it works horizontally (max Ee at the 2 ends, max Ek at the equilibrium position), but how does it work vertically now that Eg is also present? this is how i see it: setting the maximum stretch as h = 0, upon release of the mass, Eg = max (let's set max as 1 unit), Ee = 0, Ek = 0. at the bottom, Ee = 1, Eg = 0, Ek = 0. but at the middle, which is the equilibrium point, Ek should be max, and Eg and Ee should be 0, but it is half way of the unstretched position, so Ee = 1/2, and Eg is also 1/2 since it is half way between max height and min height (which i set to 0), so how can there be Ek? this is what's confusing me.