1. The problem statement, all variables and given/known data A toy rifle shoots a spring of mass 0.008kg and with a spring constant of 350 N/m. You wish to hit a target horizontally a distance of 15m away by pointing the rifle 45o above the horizontal. How far should you extend the spring in order to reach the target? 2. Relevant equations E = 1/2(k)(x)2 F = kx KE = 1/2(m)(v)2 Any relevant kinematics formulae. 3. The attempt at a solution Normally for questions like this I would equate potential spring energy to the kinetic energy, but here I am missing a velocity as well as the spring compression length so I am a little lost.