1. The problem statement, all variables and given/known data The problem concerns the collision of a particle on a rigid, fixed disk of radius R. The coefficient of friction is zero, and the coefficient of restitution is 0 < ε < 1, such that vperpendicular, final = εvperpendicular, initial . A) Show that tanαincident = εtanαfinal (completed) Where α is the angle from the velocity vector to the normal vector B) Write a program to numerically solve for the differential cross section (main problem) 2. Relevant equations impact parameter : b Scattering angle : θ differential cross section : dσ/dΩ = (b/sinθ)|db/dθ| 3. The attempt at a solution I honestly do not know where to start here. I solved this problem for hard-sphere scattering but now solving for the impact parameter, b, leads to a dependence on α, which vanished in the hard-sphere case. Any tips on getting this started would be appreciated.