interaction in the snow. Tat interaction results in the snow spraying in the air from the board scraping off the top layer of snow. Even though the snow does not typically push back in one particular spot, the sideways skid creates many small bits of centripetal force that, when added up, create enough friction (which is a force) to make the board turn. Centrifugal force is a center-fleeing force. It is the outward-pushing force, felt by riders while moving in a circular motion (i.e., the arc of a turn). However, there is no real outward force acting, and centrifugal force is therefore known as a fictitious force. Te centrifugal force is often mistakenly thought to cause a body to fly out of its circular path when it is released; instead, it is the removal of the centripetal force that allows the body to travel in a straight line.
ANGULAR MOMENTUM In terms of snowboarding physics, angular momentum is the direction a rider would follow if the board suddenly broke loose from a turn. Te angular momentum, or tangent of a curve, is oriented perpendicular to the radius of the curve at that point – assuming that the slope is absolutely flat. In maintaining a turn, a snowboarder must constantly overcome the tendency of the snowboard to go in the direction of the tangent, instead of continuing to follow the arc of the turn. Te strength of the tendency to break away from a turn is related to the speed and mass of the object and the radius of the turn. Tink of the tangent like this: If you had a ball at the end of a string and were swinging the ball in a circle overhead and suddenly let go of the string, the path that the ball would follow would be the angular momentum, or tangent.
NEWTON’S LAWS OF MOTION Newton’s Laws of Motion describe the relationship between the forces acting on a body and the resulting motion. Tese universal laws help explain how a snowboard interacts with the snow. All moving objects, including snowboards and snowboarders, move and react according to these physical laws and principles. A few simple laws and principles help you understand why snowboards behave as they do and predict how they will respond to specific movements and terrain conditions. Sir Isaac Newton described three laws that affect all types of motion: Newton’s Law #1: An object remains at rest or continues to move in a straight line at a constant speed if there are no unbalanced forces acting on it. Tis principle is called inertia; thus, inertia is the resistance of an object to change its state of motion or rest. Newton’s Law #2: When the forces acting on a body are not balanced, the net force causes the body to accelerate. Tis is expressed as F = ma. Te net force is “F,” the mass of the body is “m” and the resulting acceleration of the body is “a.” When “F” is a lateral (sideways) force, it causes a constant change of direction instead of a change of speed, resulting in motion along a circular path. Technically, circular motion is a form of acceleration.
Newton’s Law #3: Every force has an equal and opposite reaction force. When a snowboarder stands on the snow, he or she is pulled down by the force of gravity (i.e., by the weight of the rider), and the snow pushes up with an equal force. Forces are balanced, that is, the net force is zero. Te lateral force of a snowboard pushing into the snow during a turn is balanced by the snow pushing back against the snowboard.
TheSnowPros.org CHAPTER 1: PHYSICS OF SNOWBOARDING 23
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