The physics of hockey players

Much has been written about the physics of hockey. I even have a book about it that was thoughtfully given to me for Christmas one year (since I am, in fact, a physicist). However, it struck me today at shinny that there is a parallel between basic mechanics and the development of hockey playing ability. Since I've only been playing a few years now I can easily see the stages that I've gone through so far.


First, a bit of physics. You start with the position of an object (denoted r, usually). If you look at how the position changes with time (the first derivative of position with respect to time, for all you nerds out there), that is the velocity, v. Furthermore, if you look at how the velocity changes with time (or the second derivative of position with respect to time), you have the acceleration, a.

Hockey sense seems to develop along the same lines. 

First you learn positions (r). Defence, forward. Where should I be when I'm defending? When I'm attacking? How do I get there if my skating skills are weak? Holy mackerel, can I stop in time? The play just whizzed by me, and I know I'm out of position. Where are the opposing players right now? Can I keep my head up while I'm stickhandling to see where everyone is?

On my team, I play defence, and one of my tricks is that I'm always counting (actually, subitizing) bodies by jersey colour at a glance, whether ahead of me or behind me. If I see four of my players in front of me when we're on the attack, I know I'm the last man back. If the opposing team starts to break out and I don't see five bodies in front of me I know that there is one behind me!

Eventually you figure the position part out. You skate with your head up. You start to see the players on the other team before they zoom by you. Then you naturally start to predict where they're going: you start to get a feel for velocity (v). I see the opposing centre, she always dekes left. I look up, my winger is breaking out, I lead her a bit when I pass her the puck. She's moving anyway, I'm going to bang the puck off the boards and hope it gets to the same spot she's heading toward. I see a mess of people in the neutral zone but I can pick out who is moving in which direction and try and hit her with a pass. After one of those mad scrambles in my own end, if I've been paying attention, making maximum use of my peripheral vision, I know who on my side is moving forward so I can try and hit them with a pass or even just tip the puck toward them, out of reach of the opponents.

In shinny I usually play forward. When the puck has changed hands in the neutral zone, or even when the other team is breaking out from behind their blue line, I'm watching the eyes of the guy with the puck. He's looking to see who's ready for a pass, who's got the momentum, so first of all you can see him sizing up his own forwards. So I look out of the corner of my eye, and listen too - who on the other team is already moving? That's the guy who's going to get the pass, not the guys who are standing still or looping around to change direction. The velocity of the opposing players tells me where the pass is going to go. Sometimes I can get in the way and at least derail the pass, if not actually intercept it.

The last piece of this puzzle is acceleration (a). Not only who is moving and which way, but who will be moving really fast, soon?  Who likes to loop around, who likes to pivot to keep an eye on the play, and who can stop on a dime and change direction quickly? On my team and the other team? Also, my own acceleration - important in races to the puck - can I get up to speed faster than her/him? The acceleration of my stick - in a close call, can I jab it out quickly and poke that puck out of reach? Can I get the puck to change direction (from a physics standpoint, that is acceleration), and even better, can I direct it to one of my moving players? (Acceleration and velocity!)

Negative acceleration - deceleration - is important, too. Two people are approaching the puck, if the other person is afraid of a collision and starts putting on the brakes, I will beat her to it, but only if I don't imitate her, if I keep my speed up while she's slowing down. Easy to say, hard to do.  Am I willing to use the boards to absorb some of my momentum in order to win that race to the puck? That can hurt if you do it wrong! When you're attacking and the defence is skating all-out to stay with you, slam on the brakes (deceleration!) - they will go careening past you into the corner, leaving you free to do as you wish.

So there you have the natural steps in developing hockey sense - you basically just get better at doing the calculus. First you master position, and then you start intuiting the time derivatives of the position: velocity and acceleration. As you get a feel for how everybody moves, how the puck moves, how your stick can move, how your own body can move, you get better at predicting what might happen, and being ready for it. The physics of hockey players.