Question

what is impact parameter

Answer 1

It is defined as the perpendicular distance between the path of a projectile and the centre of a potential field U(r)

Answer 2

The impact parameter is defined as the perpendicular distance between the path of a projectile and the center of a potential field created by an object that the projectile is approaching (see diagram). It is often referred to in nuclear physics (see Rutherford scattering) and in classical mechanics.