The physics
An air table is almost smooth. No outside force pushes a puck along the table. So the total momentum of the pucks stays the same in a hit.
Momentum is a vector. It stays the same along east, and along north, each on its own. Split every velocity into these two parts.
east: Σ m vx stays north: Σ m vy stays
When two pucks stick, add their momentum arrows head to tail. The sum points the way the pair moves. Its size ÷ the total mass is the pair's speed.
Two equal pucks in an elastic glancing hit leave at 90° to each other. A heavy puck can hit a lighter one at rest. It then turns by at most θ, where sin θ = m₂ / m₁.
A smooth rail pushes only straight out from itself. The part of the velocity along the rail stays. The part across it turns round and shrinks by e.
tan β = e tan α (both angles from the rail)