## Monday, November 30, 2015

### The physics of hockey sticks

At the Flyers game last Monday night I noticed four hockey sticks break over the course of the game. This number seemed so high to me, so I decided to investigate. My boyfriend is an avid sports fan and he said that the sticks used to break less often because they were made of a different material in the past.
 Image from NWSportsBeat.com

In the 1980s did aluminum hockey sticks became popular, but now composite sticks are the most popular. Since hockey sticks can bend up to 30 degrees, they can be modeled by equations for elasticity in solids. In a paper by Russell and Hunt (2009), they investigated the Young's modulus for different types of hockey sticks. The wood hockey sticks had the lowest Young's moduli (8.88 - 16.25 GPa), the composite sticks were in the middle (31 - 42 GPa), and the aluminum sticks had the greatest Young's moduli (52.62 GPa).

Hockey sticks are sold with a certain "flex" value that describes how much pressure a stick can take. The flex value means the "amount of force required to 'flex' the stick one inch" (Monkey Sports). The average flex is about 85, because it is recommended that players choose a flex value that is at least half the weight of the player. Since players put more weight on the stick during certain shots, like slap shots, the stick may break during a particularly powerful shot because of too much flex. It is interesting to think about hockey from a physics point of view because players, coaches, and manufacturers need to be aware of the physics of force and pressure in order to design good sticks.