Hello I need helpwith these questions. Consider a 1D collision between two particles. If the collision is neither perfectly elastic nor perfectly inelastic (i.e. ), in addition to the masses and initial velocities, what additional information do you need in order to calculate the velocities after the collision?

Hello I need helpwith these questions. Consider a 1D collision between two particles. If the collision is neither perfectly elastic nor perfectly inelastic (i.e. ), in addition to the masses and initial velocities, what additional information do you need in order to calculate the velocities after the collision?