Professional hockey players shoot pucks at over 100 mph, but it takes some knowledge of the physics of the puck sliding on the ice and the torque of the stick to do so. Hockey players combine wrist shots and slap shots in each game when trying to score a goal, and each of these shots requires a slightly different technique. The material of the hockey stick also factors in to how the stick will flex, or bend, when the player takes the shot.
Ice Physics
Ice is a slick surface, which allows both the puck and the skaters to glide along its surface. However, even though it is slippery, the surface of ice still provides friction against the sliding of the puck, which is why it slows down as you pass or shoot it across the ice. The more the ice melts, the more slowly the puck moves along the surface, so the player must take the condition of the ice into account when shooting the puck. Toward the end of a play period, the ice is usually less smooth than at the beginning due to the players' skates shaving off the surface and creating divots in the ice. Players must shoot the puck harder on rough ice to make it go the same distance as it would with less force on smooth ice.
Wrist Shot
Wrist shots are not usually as fast as slap shots and are taken closer to the goal. The player uses a sweeping motion to propel the puck toward the net, and according to Alain Hache's "The Physics of Hockey," the "amplitude of motion ... is about half or less than half of that of a slap shot, so the body can't build as much speed and energy during the sweep." The puck stays on the blade of the stick for 1 to 2 feet and is directed toward the net by the turning of the player's wrist. The player must press down on his stick, pushing it against both the ice and the puck, so it accumulates additional potential energy for the shot. When the player combines the motions of pushing the puck forward and allows the shaft of the stick to rebound, the puck will move toward the net at a greater speed.
Slap Shot
The slap shot is less accurate than the wrist shot, but is good to use when the player wants to achieve a very fast shot. The physics of the slap shot include the wind-up, the contact and the shot. The wind-up phase includes the player rotating his torso away from the puck and pulling his stick up and back away from the puck. The contact phase is when the blade of the stick hits the ice, then the puck, bending the shaft of the stick to accumulate potential energy. The deeper the bend in the stick, the more potential energy that is built up and the harder the puck will fly. The shot stage is when the puck leaves the blade and the stick straightens out, helping propel the puck forward.
Stick Types
Hockey players may use a full wooden stick, a one-piece composite stick, or a two-piece stick made up of a composite shaft and a wooden blade. A study by Wu, et al., looked at the role of the material of the sticks and how it affected slap shot velocity. The study found that between wood, graphite and aluminum sticks, the material of the stick did not influence the puck's velocity during the shot, but it was instead influenced by the player's strength and skill level. The study determined that the more the stick bent during the contact phase, the more force was generated and the farther the puck shot. Therefore, the material of the stick is left to player preference; none confers a specific advantage.
References
- Exploratorium; Sports Science; Shooting the Puck
- The Sport Journal; Biomechanics of Ice Hockey Slap Shots: Which Stick Is Best?; David J. Laliberte
- "The Physics of Hockey"; Alain Hache; 2002
- "Sports Engineering"; The Performance of the Ice Hockey Slap and Wrist Shots: The Effects of Stick Construction and Player Skill; T. C. Wu, et. al.; 2003
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