♪music♪ 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 funded by the National Science Foundation, explain. [natural sounds] 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.