1. The problem statement, all variables and given/known data A particle, unknown mass, has velocity v0 and impact parameter b. It goes towards a planet, mass M, from very far away. Find from scratch (? i'm not sure why it says from scratch), the distance of closest approach. 2. Relevant equations I believe this equation is relevant: Veff(r)=L2/2mr + V(r) 3. The attempt at a solution I haven't attempted this problem because I have no idea what distance of closest approach is. I looked throughout my book and haven't found anything.