1. The problem statement, all variables and given/known data m_1, v_1f m_2, v_2f m_2 = m_1 = m 2. Relevant equations KE = .5mv^2 W = F*d spring: F= -kx pot energy = PE = -.5kx^2 3. The attempt at a solution A) K + U = .5m(v_1f)^2 + .5m(v_2f)^2 - .5kx^2 .5(.1kg)(v_1f)^2 + .5(.1kg)(v_2f)^2 -.5(100N/m)(.02m)^2 B) ?? translational KE - going straight? isnt it .5(.1kg)(v_1f)^2 + .5(.1kg)(v_2f)^2 C) ?? V_cm.... ?? am i looking for how fast the center of the spring is moving? the center of the spring moved from .03 m to .1m and so ?? im lost or do I get the average speed of the two boxes which would be V_cm = (V_1f+V_2f)/2 or .5(.1kg)(v_1f)^2 + .5(.1kg)(v_2f)^2 -.5(100N/m)(.02m)^2 = Wd = (5N)(.08m) (v_1f)^2 + (v_2f)^2 = 8.4 (m^2)/(s^2) does that equal V_cm? V_cm = ( 8.4 (m^2)/(s^2) ) ^ (1/2) = 2.90 m/s D) ?? vibrational?