Monday, October 24, 2016

Slap Shot! Can you stop it?

On Saturday, I was watching the Boston Bruins play and began to think about the force needed to accelerate the puck during a slap shot. So, I went and did some research on slap shots. According to the Guinness World Records the fastest slap shot that was recorded in a competition was done by Denis Kulyash of Avangard Omsk in the Continental Hockey League's All-Star skills competition in St. Petersburg, Russia, on 5 February 2011. This shot was clocked to be traveling at 110.3 mph or 49.3 m/s. Although this is the record, I am sort of biased towards the second-place holder Zdeno Chara of the Boston Bruins, who set the record during the National Hockey League's All-Star skills competition in Montreal on 25 January 2009 with a shot clocked at 105.4 mph.  Either way both shots produce a hockey puck that is moving incredibly fast. To find the acceleration that puck experiences I started by describing the interaction as an elastic collision.  The average mass of a hockey puck is 170 g or .17 kg. The average mass of a new composite hockey stick is around 450 g or .45kg. The final velocity of the hockey stick is 3m/s. Using the conservation of momentum equation, you calculate the velocity of the hockey stick in the collision.

(Mp) (Vpuck intial) + (Ms) (Vstick intial) = (Mp) (Vpuck final) + (Ms) (Vstick final)

0 + (.45) (Vsi) = (.17) (49.3) + (.45) (3)

Vsi = 21.62 m/s

Then by finding the impulse you can solve for the force. The collision lasted for .001 seconds.

Change in momentum = sum of forces x change in time

(.17) (49.3)/.001 = 8381N

Then if you take that force and divide it by the mass of the puck you can find the acceleration that is experienced by the puck

8381N/.17kg = 49300 m/s2 or 5030.6 times gravitational force (g)

Overall, there is both a crazy amount to force and acceleration.

*In this situation, I am not considering the flex of the stick.

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