In honor of my Ovechkin's 500th goal (my favorite player on my favorite team), I decided to look into the physics behind the infamous slapshot in hockey. 

The basic physics of the slapshot include the windup that produces torque applied to the puck and the transfer of energy to the puck, but there is a lot more physics involved that launches the puck with such a high velocity. First of all, the collision with the puck is mostly elastic, but considering the huge noise produced during a shot, it is not completely elastic as some of the kinetic energy is transferred to other energy types. During the collision, the blade of the stick is in contact with the puck for hundredths of a second, creating a larger force applied to the puck since force and time are inversely related for impulse. However, one of the most important aspects of a powerful slapshot is actually making contact with the ice before making contact with the puck. This concept seems counter-intuitive since it will take away some of the momentum of the stick, but in reality it makes the shot stronger because the stick acts like a spring. Upon making contact with the ice, the blade of the stick bends backwards to a displacement of up to 3 inches from the normal position, which stores energy into the blade as potential energy. Since hockey sticks are made of materials such as wood or a mixture of carbon fiber, fiberglass and graphite, they do not bend easily so the "spring constant" is high, storing a lot of potential energy in even small displacements. When the stick makes contact with the puck, the kinetic and potential energy is transferred to the puck, sending the lightweight puck flying at a very high velocity since velocity is inversely proportional to mass for momentum. 

Because the flex of the stick is vital to the development of power during a slapshot, and even a wristshot, hockey sticks are sold with a variety of different "flex" options.