A lacrosse ball is a solid sphere composed of a hard synthetic rubber material, which allows it to be heavy enough to throw with maximum speed and momentum, yet flexible enough to bounce. There are many aspects of the ball that are related to physics.
For instance, the "grippiness" of the ball gives it the ability to spin when thrown out of a player's stick, creating centripital force, and if the ball gets spinning fast enough, let's say on a really hard shot or long pass, the ball can actually vere off normal trajectory lines and "curve". This phenomenon is very similar to a pitcher on a baseball field.
When the ball hits the turf or crossbar, it can bounce a great distance depending on the initial velocity of impact with the surface.