For a lab testing the conservation of momentum, I had to hit an air hockey puck so that it would hit another stationary puck in a glancing collision. After the pucks collided, they travel their separate ways, but I also noticed that both pucks seem to be spinning in circles as they travel on. This spinning had no effect on movement, as both pucks were only traveling in straight lines throughout the experiment. I did this a few more times and it happened every time I repeated it. What could have caused the pucks to be spinning in circles when all I did was hit one puck straight on, which then collide with the other puck?
If the collision is not perfectly along the line connecting the centers of mass of the pucks, they will exert torques on each other as well as forces. The angular momentum of the pair will be conserved, so if the incoming puck was not spinning, the pucks will exit the collision spinning in opposite directions. If the surface they slide on is frictionless, the spinning will not affect the translational motion.