dear all, i am working on a problem, but not having found the solution yet. i have a wall section (in a 2D x-y plane) on which spherical balls hit and get reflected. i know the x-velocity and y-velocity of the particle when it hits the wall. i need to calculate the impact (incident) angle of the ball on the wall. it is easy to calculate when the plane is either along x-axis or y-axis. but, my plane is curvilnear (i know the radius of curvature). can i calculate the incident angle for this curvilinear plane ? pls help. thank you.