Banking on Speed: Bobsled

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The following is the transcript for Banking On Speed: Bobsled.

LESTER HOLT, anchor: The Winter Games in Vancouver provide a chance for the United States four-man bobsled team to win its first gold medal in more than sixty years. Team members and an Olympic bobsled designer with help from a materials science researcher and a sports scientist funded by the national science foundation explain how they’ll accomplish this feat. The Bobsled got its name when it appeared in Switzerland in the 1890s – its riders “bobbed” back and forth to try to increase their speed. Today’s Olympic bobsledders use precision moves…and an intuitive understanding of physics…to maximize velocity – the speed of the bobsled as it plummets downhill.

STEVE HOLCOMB, U.S. Bobsled Team: There's more than just four fat guys getting into a sled and sitting there and hoping to win.

HOLT: By hurtling around the icy bends of the course at 5-Gs – five times the force of gravity…akin to what fighter pilots experience. Physicist – and Air Force veteran -- Paul Doherty did the Olympic bobsled run in Lillehammer, Norway --site of the 1994 Winter Games.

PAUL DOHERTY, The Exploratorium: We were being slammed first to the right at five G's and then to the left at five G's. And when you bend your head forward under five G's, which I did through one of the turns, you can't lift it – your neck muscles are not strong to lift it, and bring it back up.

HOLT: What gives the bobsled its velocity is acceleration – initially created during the powerful 50-meter push at the race start…by the team’s feet pushing forcefully against the ice.

DR. DEBORAH KING, Ithaca College: the start is where you are going to try to pick up speed. So you are getting your acceleration.

DR. GEORGE TUTHILL, Plymouth State University: The team is trying to get that bobsled moving as rapidly as possible, by applying maximum force to the track.

HOLT: Then, in a tightly choreographed succession, the bobsledders jump in – while trying to keep the sled steady, and on a straight trajectory.

Slapshot Physics: Hockey

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LESTER HOLT, anchor: One of the most popular team sports at the Winter Olympics is hockey. More than just a physical game, for scientists like The Exploratorium’s Thomas Humphrey, a physicist funded by the National Science Foundation, hockey is a showcase for physics on ice – especially when it comes to hockey’s hardest shot: the slap shot.

HOLT: In a game known for hard hits, it may be the hardest one of all. The violent collision between stick and puck that produces one of the fastest projectiles in the Olympics: the slap shot.

ZACH PARISE (U.S. Hockey Team): For me, probably about 85, 90 miles an hour, not very fast.

HOLT: More than a feat of physical strength, the Olympic slap shot is a showcase for the physics of elastic collisions – the nearly perfect transfer of kinetic energy from a hockey stick to a frozen six-ounce rubber puck.Thomas Humphrey is senior scientist at The Exploratorium in San Francisco.

Dr. THOMAS HUMPHREY (The Exploratorium): Two Hundredths of a second is the amount of time that the stick is in contact with the puck. But the average force on the puck is about 100 lbs.

HOLT: To see slap shot physics in action, we went to one of the best and brightest players in the world. Julie Chu is a Harvard grad and two-time Olympic medal winner who will be going for her third medal as a Team USA forward in Vancouver.For this experiment, Chu allowed us to film her slap shot with a "phantom cam," a special high-speed digital camera that can shoot at up to 15-hundred frames per second.

JULIE CHU (U.S. Hockey Team): The high-speed camera is incredible; like we know that we’re flexing the stick a bit, but you might not get a sense that it bends that much under your power or the weight that you’re throwing into the puck.

CHU: Oh, that’s awesome.

HOLT: The first step to Chu's slap shot is the wind-up. Watch how she rotates her upper body until the stick is high overhead, then how she transfers her weight from back to front skate, swinging at the puck with maximum velocity.

Dr. HUMPHREY: You get the stick moving first. It's got a lot of momentum from all your muscles and your action there, a lot of momentum, and that momentum is transferred to the puck.

HOLT: The second step is the key to the slap shot’s speed. During the swing, Chu's stick actually strikes the ice before it hits the puck. Instead of slowing the shot, it amplifies it - by adding flex to the stick, and loading it with potential energy.

Dr. KATHARINE FLORES (Ohio State University): When you let the-- the stick snap back-- it's going to put all of that energy into the puck. And that energy's going to translate into the velocity of the puck.

PARISE: The flex and the whip and the stick almost shoot’s the puck for you. And if with the good form, and the proper form it gives the puck a lot more velocity.

HOLT: Adding to the snap, most Olympians today use sticks made from aluminum, carbon graphite and other materials that are stronger, lighter, and much more flexible than wood.

Dr. FLORES: When we saw it on the test frame, we were actually applying about 300 lbs of load to the stick, and deflecting it through about three inches of displacement.

HOLT: The final step to the slap shot is the follow-through, which ends a bit like a wrist shot. Watch how Chu uses her wrists and the curve of the blade to impart spin to the puck. Like a gyroscope, the spin helps keep the puck stable in flight.

Dr. HUMPHREY: At the very end of a slapshot you also do a little bit of a wrist shot actually to get the puck rolling off the blade. So you have a little bit of control on it, not as much as you have with the wrist shot.

HOLT: In slow motion, slap shot physics is revealed. In real time, it unfolds almost effortlessly.Announcer: Darwitz back to Chu, walking on, firing, she score!

CHU: When you hit the puck just perfect on the slap shot, it really takes off with some zing, you can just feel it.

HOLT: Especially when the slapshot finds its way to the back of the net.

Science Friction: Curling

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The following is the transcript for 'Science Friction: Curling'

LESTER HOLT, anchor: Curling has been in the Winter Olympics since 1998, but still seems a little strange to most of us. We had John Shuster, captain – or “skip” – of the U.S. Curling Team in Vancouver, explain this unusual sport for us, while scientists funded by the National Science Foundation explain how friction makes it all work.

Curling. Perhaps the most unusual sport in the Winter Olympics. A huge rock is thrust down a long sheet of ice. Two players sweep a path in front of it, guiding it to the center of the target, called the “house.” At the end of play, the team with the most points – the most rocks closer to the center -- wins. Olympic bronze medal winner John Shuster is a life-long curler.

JOHN SHUSTER (U.S. Curling Team): My family is big into curling. I remember throwing you know, a rock at the curling club when I was, you know, probably six or eight years old.

HOLT: Getting the curling stone from the start to the house is all physics, starting with the push-off against what’s called the “hack.”

SHUSTER: What you're able to do off of here is to position your foot to allow yourself to accelerate out of the hack with the curling rock. You can push out of this hack with a very high amount of force and you know it's going to transfer into the curling rock.HOLT: Then the sweepers move in. Curlers: Hard!

SHUSTER: This is like a synthetic material that has just a little bit of abrasiveness. Curlers: Yes!

SHUSTER: Curling terminology as far as sweeping goes, it’s anything that you could consider, versions of “yes”…Curlers: Yeah!

SHUSTER: But usually it’s “hurry” and “hard”…Curlers: Hard! Hard!

SHUSTER: You want them to, you know, push harder.

HOLT: To help the stone go farther and straighter.

SHUSTER: Back in the old days, people used to think when you swept in front of a rock you'd clear out snow and frost and that allowed the rock to go further. Well, after we got the snow and frost elements removed when we moved indoors, now all of the sudden you're sweeping a rock and its even affecting it more, it's going fifteen feet further.

HOLT: That’s because sweeping wasn’t just removing the snow and ice, it was reducing the friction between the stone and ice. The rapid back-and-forth of the sweeping generates heat.

Dr. SAM COLBECK (U.S. Army Cold Regions Lab): It all just comes down to this [rubs hands] yeah, it comes down to this. They’re warming that ice up maybe enough to generate a melt-water film.

HOLT: A melt-water layer that reduces friction, creates a literal path of least resistance for the stone to glide on more easily. Friction is reduced even further by another characteristic of curling ice: bumps.

IAIN HUETON (Ogden Curling Club, Utah): All of the other ice sports have a smooth, Zamboni surface effectively, and curling requires that the surface of the ice be roughened.

HOLT: Spraying water does the trick.

HUETON: And then when it lands on the ice, it freezes up and forms these nice pebble-shaped bumps, and if you look at it, it looks like an orange peel, that kind of roughness is about the right texture, and that gives us the surface we need.

HOLT: But wouldn’t the bumps, like mini-speed bumps, just slow the stone down? Actually, it’s the reverse: the “points” reduce the total ice surface the stone rides on. The less surface contact, the less friction. And there’s another reason:

HUETON: If we're on smooth, frozen Zamboni ice in an arena, if that's making a nice seal with the bottom of the stone, you're going to eventually form a vacuum as the stone moves across the ice, and it really slows it down. You’ve got air pressure pushing on the stone. Whereas, if you can have it riding on a few points then it's going to slide more smoothly and you won’t get any kind of a vacuum forming and it’ll go roughly twice as far.

HOLT: The make-up of the stone itself plays a role.

SHUSTER: Curling rocks are 42 pounds of granite, and actually the granite only comes from the island called Ailsa Craig that's off the coast of Scotland.

HOLT: This type of granite is “hydrophobic” – it resists water. That means it will absorb very little of the melt-water layer at the surface. Absorption could reduce the lubrication helping the stone glide toward the house. As the curling stone approaches the target, there's a good chance another team's stone is in the way. When the stones collide, another wonder of physics takes place: momentum exchange.

Dr. GEORGE TUTHILL (Plymouth State University): When you see the collision of two curling stones you’re seeing the transfer of kinetic energy between them and you’re also seeing the transfer of momentum, the product of mass and velocity between them.

HOLT: Well, there you have it: the basic physics of curling. From the hack to the house, from the coefficient of friction to the transfer of kinetic energy, curling is a sport that attracts the crowds and delivers excitement with a bump.

Five Things to Know about Curling

VANCOUVER (AP) -- Sweeping. Broomstacking. The hog line.

No, we're not talking about tidying up a pig pen. These are terms from curling, an ancient winter sport at the Vancouver Olympics.

Here are five things to know about curling:

1) The sport often is compared to shuffleboard on ice. The Olympians play 10 ends, or innings (yes, like baseball), and the team with the most points at the end wins.

2) After a 42-pound granite stone is sent sliding down the ice, two players use sweeping motions to control it _ to make it go faster or slower, or to change its direction, or "curl." The goal is to get the stone as close as possible to the center of a series of concentric circles.

3) Don't even think about knocking the curlers for not being athletes. Although curlers like to have fun, counting the social aspect of the sport as a big part of the experience they love, curlers around the world have taken their fitness to a new level in preparation for these games. They have personal trainers, high-intensity training camps, sports psychologists and more. The teams that don't work out hard off the ice are the ones that fall behind everybody else.

4) Behave yourself. This sport, dating to 15th-century Scotland, prides itself on a tradition of sportsmanship and good manners. The Chinese women didn't talk to the media after Sunday's practice in order to keep their focus, and it caused an uproar of sorts. On Monday, when they passed the media, they smiled and said "hi."

5) The terminology is foreign to say the least. There's broomstacking, the post-match ritual of heading to the lounge with the opponent for a friendly drink. (Traditionally, the winners buy the beers.) The "button" is the inner-most circle within the "house" _ the area the stone must cross into to be in play.

And don't forget the "hog line." That's the first far line the stone crosses just before reaching the house.