Another important aspect of hockey is shooting. Shooting a puck requires a good combination of power and accuracy in order to score in today's game. With the technology of sticks and strength of players improving, the quality of shots in hockey today are at an all time high. On this page, the physics of shooting a puck will be discussed.
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Features of a Stick
When choosing a hockey stick, many factors need to be taken into account.
Blade Curvature:
One of the key features of a hockey stick that affects puck control is the curvature of the blade, which acts as a self-centering mechanism. When shooting a puck, the curve of the blade forces the puck to sit in the bottom part of the curve of the stick for a moment before flying of the stick. The benefits of having a curved blade is it allows for more consistent shots because the puck will tend to leave from the same part of the stick for every shot. Also, a curved blade allows players to more easily put spin on the puck which gives it gyroscopic stability during flight (saucer pass) which will make the puck more likely to land flat on the ice. Finally, playing a certain position and personal preference lead players to choose certain curves over others. |
Blade Face:
Another key feature of a hockey stick is the face or loft of the blade which is the tilt angle of the blade, visible when looking at the stick from directly above, as seen in figure 2. A larger tilt angle of the face makes the puck lift off the stick and rise more easily when airborne. Again, how much tilt of the face comes down to the personal preference of the hockey player. |
Flex:
The final key feature of a hockey stick is the flex of the stick which is how flexible or how stiff a hockey stick is when force is applied on it. Essentially, flex helps the speed and power of shots because when a player starts to apply a downward force on a stick, the stick will start to bend which creates elastic potential energy (as seen in figure 3). Therefore, when the player follows through with the shot, the stick will release the puck in a "spring" like action which creates kinetic energy that accelerates the puck even faster. Even though a more flexible stick allows for more "spring" action, the player should still have some resistance from the stick so the stick does not snap due too much force being applied. |
Mechanics of Slap Shot:
For all shots, it requires the stick to apply a greater applied force on the puck than the frictional force that are resisting the puck's movement. Since hockey is played on ice, the coefficient of friction between the puck and the ice is extremely small and thus indicates that the stick only requires a small applied force in order for the puck to move. In hockey, there are three different types of shots which consist of a wrist shot, a backhand and a slap shot. Here, slap shots will be the main shot that will be focused on. Slap shots are the most telegraphed shots in hockey which require the player to start by raising the stick up above their body and therefore creates gravitational potential energy. The player then forcefully strikes the ice about 5-15 cm behind the puck and uses their weight to bend the stick and create elastic potential energy. Finally, when the face of the stick reaches the puck, the player will rotate their hands and shift their weight in order to transfer the stored energy from the stick into the puck to create kinetic energy. This energy transformation can be seen in Figure 4.
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NHL Example:
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Zdeno Chara is a Slovak defenseman who is currently the captain of the Boston Bruins. Chara won the James Norris Memorial Trophy in 2008-09 season for being the best defensemen in the NHL and is currently the record holder for the NHL All-Star Skills Competition hardest shot with a 108.8 mph slap shot speed as you can see in the following video. But the question remains, how much force did it take for the puck to be shot from the top of the circles into the net at a final velocity of 108.8 mph?
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As shown by the calculations below, it took 18.9 N to move the puck at a final velocity of 108.8 mph
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Physics Behind Hockey © 2015
Matthew Richards
Matthew Richards