Moving fast on ice
RALEIGH — Hockey is one of the fastest sports on Earth. Players can travel as fast as vehicles, up to 25 miles per hour. And when a player shoots a slap shot, the puck can scream along the ice at 90-100 miles per hour.
"It’s a challenge playing at that speed with so much going on,” says Rod Brind’Amour, an assistant coach with the Hurricanes.
Brind’Amour played 20 seasons in the NHL with the St. Louis Blues, Philadelphia Flyers and the Hurricanes. He was the Hurricanes captain when the team won the Stanley Cup in 2006.
“You’ve got to know not just what you are doing but what everyone else is doing and where everyone else is, so it’s all about awareness, Brind’Amour adds. “You have to know where they are going, anticipating where they are going so you can get the puck there in time or your body there in time.”
Making split second decisions
But it’s not just practice and hard work that helps the Carolina Hurricanes win in this fast and frozen sport. It’s science. We spent some time at a Hurricanes practice to learn more.
“There’s a lot going on in a split second, but these guys are so good it just happens naturally now,” says Brind’Amour.
Hurricanes goalie Scott Darling agrees the game is lightening quick and there’s not much time to think.
"There’s a lot of information being thrown at you as a goalie because you have got to worry about the shooter, about pass options, about what could go wrong and what happens if it becomes a broken play and that’s just a start,” says Darling. “There’s also a chance the entire play could be a screen trying to sneak something by you. You have to watch and plan for it all.”
Hockey tricks rely on physics
So let’s look at a few key components of a hockey game to understand how science is involved. First, there’s the slap shot. It’s one of the most exciting moments in hockey as well as a dramatic example of how multiple types of energy are used. The player turns sideways to the goal, winds up with the stick behind him, and then swings through the puck.
The power for the shot comes from the player transferring his weight from the back legs through the body, down the arms and right through to the stick. The moving player and the moving stick are examples of kinetic energy, which is the energy of movement. But Rod Brind’Amour says if you watch closer, there’s more to the shot than that.
“So obviously it’s a big windup, but a lot of people may not know that you’re trying to hit the ice first,” Brind’Amour admits. “That’s so you can bend the stick because the stick is actually doing the work."
The bent stick is an example of potential energy, which is the energy stored in an object. When the stick actually hits the puck, the energy stored in the bowed stick is converted to kinetic energy and released into the puck. The overall motion of the shooter combined with the stick snapping back is what gives the slapshot so much power.
“And as that comes through, that torque on that stick is going to make that puck go where it wants to go or the speed it wants to go,” says Brind’Amour, who played center during his 11-year NHL career. “Now, the bigger, stronger guys can get a little more torque and little more speed on their stick because they can get a little more bend.”
The hockey stick matters
And it turns out there are different types of sticks, which allows players of different heights and weights to maximize the amount of torque a stick can provide in a slap shot.
“I use a whippy stick because it’s easier to move,” explains Derek Ryan, who plays center for the Hurricanes. “But guys like Justin Faulk use a stiff stick, because if you have a lot of upper body strength you use a stiffer stick to have a harder shot thanks to the physics of the stick.”
But there are many shots taken in hockey that are closer to the goal. Players call them flicks, or wrist shots. Brind’Amour says torque is still important.
“There’s no wind up because the puck is right on the stick, but they are pushing right into the ice to bend the stick and have the stick do the work,” he demonstrates, holding a stick and pushing it down before flicking a puck up against a wall. “It’s still the whip on the stick that's getting the work done.”
The wrist shot is an example of what’s called projectile motion. It describes how an object propelled through the air is influenced by gravity. As the player snaps his wrist, the puck rolls off the blade and towards the target. The longer the puck is in contact with the stick, the faster it spins when it leaves the stick. That spin keeps the puck on target even though gravity is pulling it down.
“You’re wanting torque but you’ll move it on your stick depending on where you want to shoot it,” explains Brind’Amour. “Guys will pull it in to get more torque, in here to get that bend, guys like it depending on the curve of their stick and where you release the puck off of the blade.”
Passing the puck
Finally, what about passing the puck? It’s one of the most important skills in hockey. Passing involves speed, accuracy and a vision of what is happening on the ice.
"The Great One," Wayne Gretzky, alluded to the science principle involved here when he said while playing a game that he would never go to where the puck is but he would go to where the puck is going. Passing is an example of what’s called velocity vectors in physics.
A vector is a quantity with more than one piece of information. The players and the puck itself all have speed and direction. Putting the vectors together shows where the puck needs to go to complete the pass. Of course hockey players do this instinctively… Brind’Amour says a lot goes into passing in that split second, even though it looks pretty routine to the average fan.
“There’s the pace of the pass and the curve of the pass,” says the ‘Canes assistant coach, who adds players also have to think about the players' speed relative to each other and how the player and stick are positioned. “So if a guy is on his forehand I can fire it hard, meaning I don’t have to lead him too much. But if he is on his backhand, where it is a harder pass to accept, I better put a little more touch and I may need to lead him a little more so he can skate into it.”
A lot of energy and motion are working together on the ice during a hockey game. The skilled players make it look easy, but the details in these physics principles are key to building stored energy in the stick, gaining torque for the puck and ultimately scoring that goal.