To my understanding when an elastic ball (which can perfectly deform) collides with a hard surface, they exert an equal and opposite force on each other. At some point, the ball's velocity must be 0. However, at this point (when velocity is 0) how can the floor be applying an upward accelerating force (beyond the normal force that only counters the weight force)?
However, if the balls got deformed, I understand that the elastic force will push it off the floor. That all makes sense until I thought about Newton's cradle when you have 2 steel balls smacking into each other. It sure doesn't look like the steel is deforming a whole lot.
So, does the steel actually "deform" and are elastic collisions in general possible without temporary deformation?