When a theoretical prediction is made, it’s nice to receive independent confirmation for it. In 2002 I had laid a simple physical model to explain a phenomenon known to every hockey player: in a slap shot, the puck goes faster if the stick hits the ice before the puck. The crude model predicted that a 100 mph slap shot would only go about 70 mph on a direct blade/puck hit [1].
Thanks to David Larochelle and Vincent Beaumont of Université Laval, we now have a better grasp of what goes on during a slap shot, as well as support for the original predictions. With professional software used by mechanical engineers to simulate complex mechanical systems, they designed a realistic framework for a slap shot. Using realistic values of stick parameters (dimensions, shape, stiffness), applied force and velocities, the results closely resemble what is seen on slow-motion videos replays of real slap shots:
1.Animation 1 : four different points of view of a slap shot with a direct blade-puck contact. Final puck velocity : 62 mph.
2.Animation 2 : same conditions as above, but with the stick hitting the ice before the puck. Final puck velocity : 107 mph.
3.Technical data and details of the simulation.
An effect not seen in the previous model is the 2 stage acceleration of the puck during a slap shot. Notice the brief midway hiatus in the graph bellow: the first part is when the stick blade is in contact with the puck but also the ice; in the second part, it’s only stick against puck. The puck first accelerate during the sweeping motions of the blade against the ice, then the flexed stick releases its potential energy to give a second boost to the puck. It’s a bit like a 2 stage rocket!
References: [1] A. Haché, The Physics of Hockey.
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