1. The problem statement, all variables and given/known data A force field in 2-d F~ = −kr(rˆ) with U(r) = k(r^2)/2 acts on a particle of mass m. The particle is now in a non-circular orbit. In terms of the particle’s angular momentum L and energy E, d) What is its closest approach to the origin? e) What is its furthest distance from the origin? e) What is its furthest distance from the origin? I am confused on how to start this problem. I can't switch my variable so that I get an equation for phi.... Can someone help me out starting this off? Thanks!!! 2. Relevant equations E = T + U T = L^2/(2r^2) b/c dr/dt = 0 U = Kr^2/2 3. The attempt at a solution I tried to do the above and solve the r^4 + ....r^2 + .... = 0 quadratic, but I can't. Can someone please help me?