Short track speed skating, the fastest self-propelled sport in the Winter Games, illustrates all of Newton's First Three Laws of Motion: (1) An object at rest will remain at rest unless an unbalanced force acts on it; (2) a force acting on a object produces an acceleration of that object; and (3) for every action, there is an equal and opposite reaction. Using high-resolution Phantom Cam video of Olympic short track skater J.R. Celski, NSF-funded physicist George Tuthill explains.
Blade Runners: Short Track Speed Skating
LESTER HOLT, Anchor:
The U.S. Speed Skating team has two best hopes against a powerful South Korean team that took three of a possible four golds in Torino –Apolo Ohno and J.R. Celski, an 18-year old world champion in his first Olympics. Speed Skating is all about force and movement, what in physics are known as Newton’s First Three Laws of Motion. Celski and George Tuthill, a physicist from the National Science Foundation explain.
HOLT: It is the fastest self-propelled sport in the winter Olympics...Speed skating.
J.R. CELSKI, U.S. Speed Skating Team – Short Track: When we’re at full speeds, we’re up at speeds of, I don’t know, 35 or 45 miles per hour. It’s pretty crazy for us to be going that fast – to be able to keep the speed and to be able to pass and maneuver around other people at the same time.
HOLT: Which is what makes short track speed-skating part sprint on ice, part demolition derby.
CELSKI: In this sport, if you do bump into somebody, you’re more likely to get disqualified.
HOLT: To win the race, a short track skater has to follow the rules of the sport – and the laws of physics: Newton’s First Three Laws of Motion. Starting...with the start.
GEORGE TUTHILL, Plymouth State University: When the skater is poised at the start, coiled up and ready to go, that skater is at rest; there is no tendency to move. Newton’s first law tells us that an object at rest will remain at rest unless there’s a force acting on it.
HOLT: J.R. Celski is a U.S. Olympic short track speed skater.
CELSKI: What we do is dig our front foot in with the tip of our skate and plant the back foot in with the whole blade.
TUTHILL: The skater sets the blade into the ice, leans over, digs in his skate, pushes straight back and accelerates forward.
HOLT: Which brings us to Newton’s Second Law.
TUTHILL: Newton’s Second Law of Motion says that when a force acts on an object, it produces an acceleration of that object – it changes the object’s motion. Right there. Second law of motion– a force on an object produces an acceleration.
HOLT: The greater his mass – that’s the sum of all matter in his body and equipment – the more force Celski must generate to accelerate down the track.
HOLT: And Newton’s Third Law explains how that works.
TUTHILL: The third law of motion is sometimes stated as “for every action, there is an equal and opposite reaction.” So if the skater pushes on the ice, exerting a force on the ice, then the ice pushes on the skater, exerting a force on the skater. The harder he pushes, the more rapidly he’ll accelerate down the track.
HOLT: Like a sprinter off the block.
CELSKI: You know, it’s more like a track start. We basically take, four or five steps just planting our feet solid, solid, solid and it’s just like running. Expect we’ve got these long blades on our feet.
HOLT: Propelling the skater faster and faster, straight down the ice.
HOLT: And according to Newton’s First Law of Motion, Celski – an object in motion – will tend to stay in motion…will keep moving in a straight line…unless some forces move him in another direction – say, around a turn.
TUTHILL: That force comes from the skater pushing on the ice, to the outside of the turn, so that the ice can push the skater to the inside of the turn.
HOLT: Turns are tight.
CELSKI: We’re doing a complete 180-degree turn around a radius that’s really sharp.
HOLT: To make tight turns, short track skaters push on the ice so hard their blade edges “bite” into it...etching tiny trenches for the blade edge to ride in around the turn, so it doesn’t slip and skid across the slick track surface...which usually works.
HOLT: The winner of a short- track race? The skater who makes best use of all three Laws of Motion to cross the finish line first.
Science Activity (Grades 6-9) from Lessonopoly
BLADE RUNNERS: SHORT TRACK SPEED SKATING
Objective: Understand the laws of physics which determine the outcome of a speed skating race.
This activity is intended for an assignment after the viewing the NBC Learn BLADE RUNNERS video clip. Speed skating is a race around an oval track. The winner is the skater who can push backwards with the greatest forces on the ice so that the ice reacts with a propulsion force (Newton’s Third Law) on the skater. The greater this propulsion force is, the greater the acceleration of the skater (Newton’s Second Law). Another factor is in keeping forces just right while making a turn so that the skater neither falls outwards or inwards (Newton’s First Law).
Questions to Investigate:
(1) Will a shorter skater have an advantage over a taller skater?
(2) Will a heavier skater have an advantage over a lighter-weight skater?
Roll a cart across a flat surface. As it moves, give a small nudge to the front of one of its sides to make it turn. Repeat this with a cart with more mass, but with the same speed. Which cart is more difficult to turn? (Which one needs the bigger force to make it turn? Which question above does this information help you answer? What preliminary answer would you give? (Remember this is a preliminary answer, you don’t have ALL the facts yet.)
Roll a cart across a flat surface. As it moves, give a small nudge to the front of one of its sides to make it turn. Repeat this with the same cart with, but with greater speed. Which cart is more difficult to turn the faster cart, or the slower cart? Which question above does this information help you answer? What preliminary answer would you give? (Remember this is a preliminary answer, you don’t have ALL the facts yet.)
Sit on or in a wagon or any thing with that will move when you push on the ground behind you. (A skateboard or roller skates might work, but you have to be able to keep your balance.) Propel yourself with a stick pushing to the rear. Repeat this with a shorter stick. Which stick gives you the greatest acceleration? Which question above does this information help you answer? What preliminary answer would you give? (Remember this is a preliminary answer, you don’t have ALL the facts yet.)
What other tests can your think of that would help you answer the two questions above? Think of the many other things that can possibly affect the skater’s performance.
When you tune into the 2018 Winter Olympics next month, you'll see plenty of painstakingly picked pieces of clothing. In some cases, the outfits do more than just make competitors look snazzy: They can actually help them go faster.
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