How would a plane hitting a ball move (opposite of Pong)? When a moving ball hits a stationary plane at an angle of incidence to the normal, it bounces away at the same angle (the angle of reflection), which is commonly understood.
My question is 1) What would happen if the reverse happened - i.e. a moving plane hit a stationary ball at an angle incident to the plane (this is the view of the first scenario relative to the ball) - would the plane bounce away with an angle of reflection the same as the ball would? How would the ball move?
This question is less important - 2) Going back to the original scenario, say the plane was moving (like in a game of pong) what are the equations that describe how the motion of the ball would change?
Thanks!
 A: Check the principle of relativity of Galileo (there are no absolute velocities, only relative ones). Both scenarios are the same and the only difference is how you choose to a stationary frame.
One usually assumes that the surface/wall doesn't move at all, given the eventual very high mass (compared to the ball), to simplify the analysis.
A: The first thing to note is that the angle of incidence and refraction are equal only for elastic collisions.
In such a case, the kinetic energy and momentum of the ball-plane system will be conserved.
The motion of the plane is a factor on how the ball moves. Let us assume here that the plane has a mass significantly greater than the ball.
The angle of incidence of the plane ball collision is measured with respect to the normal vector of the plane. So if the plane is traveling with a velocity normal to itself, the angle of incidence is 0. For achieving any other angle of incidence, the plane must hit the ball while traveling at some angle with respect to its normal vector. This angle the plane travels at is the angle of incidence for this case.
Assume that the collision is elastic. Conserving kinetic energy and momentum of the system, you will find that the ball gains a velocity much greater than the plane's at an angle that is equal to the angle of reflection, but on the other side of the normal to the plane. The plane slaps the ball away, and itself slows down or changes direction only marginally(the plane will change direction if the angle of incidence is non zero).
For example, take the plane tilted at whose normal is +45° with the positive x axis. If it travels in the x direction, and hits a ball, the ball will will be 'slapped' upwards and the plane would gain a minuscule downward component of velocity(and also lose some of it's x direction velocity). 
