The Physics of Slapshots and Mid-Ice Collisions

This microscopic wet layer and other physical properties of ice make a sharpened skate on ice one of the fastest non-motorized ways of propelling the human body. Though downhill skis move fast, the friction between a waxed downhill ski and snow is ten times greater than that between a steel skate blade and ice.

Using the magical surface of ice to combat friction, hockey players are able to generate incredible amounts of energy. Hache calculated that 180-pound NHL veteran Paul Kariya had more kinetic energy while skating at full speed than does a charging National Football League lineman of 300 pounds. He also calculated that a hockey player’s pads and flesh will compress as much as four inches during a collision with another player.

A goaltender on a series of teams since his youth, Hache devotes a chapter of his book to facts about that position. A goalie’s huge leg pads and other equipment cover 60 percent of a shooter’s target, the 4-by-6 foot goal made of red pipe and netting. Those leg pads, which cover 20 percent of the net space all by themselves, are made of leather and light synthetic padding because a hard, plastic shell would allow the puck to bounce too far.

Hockey players have blasted slapshots faster than 100 miles per hour using a three-stage process, Hache wrote. First, a player rotates his or her torso and stick in an accelerated motion toward the puck. Next, the stick blade touches the ice and the puck as the stick bends for a fraction of a second, storing energy like a loaded spring. The puck accelerates off and the stick returns to its original shape as the player completes the swing. The puck rockets toward the goal as the player converts angular momentum (stick and torso swing) to linear momentum (the puck traveling a straight course for the goal).

Players mastering this technique include Shea Weber of the Montreal Canadiens, whose slapshot was clocked at 106.5 miles per hour at the 2020 NHL All Star Game.