# Snowboard surfer.

This pro snowboarder uses more than talent to surf the slopes. Here's how Newton's Laws of Motion help her master her sport.

Leslee Olson's idea of a good time is to strap herself onto a snowboard and surf down a snow-covered mountain at speeds over 65 kilometers (40 miles per hour). Whoa! Is she kidding? Not at all. "It feels so natural and it's so much fun," says the 19-year-old from Bend, Oregon.

Olson's confidence isn't surprising. She's the world's No. 2 ranked female snowboarder, sponsored by Burton Snowboards. And she's training to compete in the 1998 Winter Olympic Games in Nagano, Japan--where snowboarding will debut as an Olympic sport.

OLSON'S SECRET ALLY

What makes Olson so good on her board? Experience for one. She's been snowboarding since she was 9 and competing since 11. She also has a hidden ally on the slopes--Isaac Newton. Not literally, since the great English physicist (1643-1727) is long gone. But Newton's Laws of Motion help explain the science behind Olson's outrageous snowboard tricks.

For example, Olson loves to compete on the half-pipe, a 12-15-foot-high U-shaped structure made of hard-packed snow. She pushes off the top of one side of the U and flies down the pipe and up the other side. Then she lunges into the air and performs flips and turns before coming back down--and up the first side again.

Helping her maneuver is Newton's First Law of Motion (also called the law of inertia): An object at rest tends to remain at rest, and an object in motion tends to continue moving at a constant speed and in a straight line unless acted on by an outside force. Using the law, Olson has soared as high as 2.5 meters (8 feet) in the air during a halfpipe competition! Unfortunately, an outside force pulls Olson down fast--the force of gravity.

Gravity is Earth's invisible downward pull on all objects--including snowboarders. How does gravity work? Every object in the universe exerts gravity on every other object. The amount of gravitational force between objects depends on their mass, the amount of matter an object contains. The greater an object's mass, the greater its gravitational pull. Because Earth is so huge, its gravitational pull is strong enough to tug Olson down before she can jump even higher.

CARVING A TURN

Besides the halfpipe, Olson also competes in slalom races. She zigzags around gates speeding down a race course. Since speed is critical, it's vital that Olson turns her board as quickly as possible.

"The best way to do that is to `carve' your turns," she says. Carving is leaning into a turn so the snowboard glides downhill on one edge, like a knife blade carving the snow. This reduces friction, an opposing force between the board and the ground that slows Olson down (see sidebar).

Carving illustrates Newton's Second Law of Motion: An external force on an object causes the object to accelerate in the direction of the force. When Olson leans into a turn, the weight of her body creates a force that causes her snowboard to move faster in the direction of the turn. So if Olson wants to turn left to swoop around a gate, she leans her body to the left and the snowboard swoops in the same direction.

THE FINISH LINE

Whether she spins in the air above the halfpipe or zooms around gates in a slalom race, Olson loves to perform on her snowboard. But every snowboarder has to stop--and that's where Newton's Third Law of Motion rules: For every action, there is an equal and opposite reaction.

Olson stops quickly through a quick and sharp perpendicular or sideways turn. This prevents her from falling over. "If you start to turn gradually, you're going to have trouble maintaining your balance," says Jearl Walker, a physics professor at Cleveland State University. "You need to suddenly turn the board and grind into the snow."

According to Newton's Third Law, when Olson pushes into the snow, the snow pushes back with equal force. The collision between the snowboard and the snow brings her to an abrupt halt.

Here's where the First Law of Motion kicks back in. Remember, an object at rest remains at rest unless acted on by an outside force After a tiring day on the slopes, no outside force can budge Olson--not even her coach.

RELATED ARTICLE: Fact OR Friction

On her snowboard Leslee Olson works with and against friction. Friction is the invisible force between two surfaces rubbing against each other that slows down motion.

If you run down a school hallway, friction between your sneakers and the floor stops you from sliding like a snowboarder. Likewise, at the end of a run, friction between microscopic bumps on Olson's snowboard and irregularities in the snow help stop her.

When it comes to downhill racing, friction also slows Olson's speed. To overcome friction, she relies on snowboard design. The base or bottom of snowboards is covered with P-Tex, a high-density polyethylene or light plastic that is easy to lubricate with wax. Snowboards are waxed to create a smooth fast trip down the slopes.

The less contact there is between surfaces, the less friction. That's why Olson "carves" her snowboard when whipping turns. She angles the board so only one edge slices through snow, like a knife slicing butter.

The most common source of friction is air. When Olson flies out of a halfpipe for an "air-raising" stunt, air pushes her back and slows her speed. She crouches and "hugs" her board to reduce the surface area of her upright body pushing against air. The result: slick sailing, plus high points for a smooth stunt.

RELATED ARTICLE: handson science

* 2 pieces of stiff cardboard (8 1/2 in. by 11 in. each) strip of cardboard (1 in. by 2 in.) tape

* books

* pencil and paper

WHAT TO DO

1. Tape the two pieces of stiff cardboard together to make a ramp that is 22 inches long.

2. Make two stacks of books, one I foot high and the other 6 inches high. Place the stacks side by side. Prop the cardboard on the books at an angle.

3. The cardboard strip is your "snowboard." Hold the strip at the top of the ramp and then push it down.

4. How can you make your snowboard go faster? How can you reduce friction? How does your snowboard's shape and weight affect its speed? Would bending the board make it move faster?

5. Think about various materials to add to your snowboard to increase its speed (tape, petroleum jelly, etc.).

6. Test your improved snowboard. Repeat step 3 three times.

DON'T STOP NOW!

CONCLUSION

What design factors help make a fast snowboard?