Newton's Laws and Skiing


How can Newton's Three Laws be used to explain skiing? Please help me!!


Newton's laws involve forces and velocity, which is speed with a direction indicated. Skiing illustrates all three of Newton's laws.

The first law says that an object which is subject to a total force of zero will move in a constant speed in a straight line. A skier is subject to two main forces, gravity and friction. Gravity tends to pull the skier down the hill and friction between the skis and the snow and between the skier and the air through which she is passing creates a force that is directed opposite the velocity. If a skier points her skis straight down the hill gravity will make her go faster and faster until the force of friction equals the part of the gravitational force directed along the slope. At that point the total force along the slope becomes zero and the skier goes along at a constant speed in accordance with the first law.

The second law says that the rate of change of an objects velocity, called the object's acceleration" is proportional to the total force on the object. In fact the proportionality constant between force and the acceleration is the mass of the object. If the skier turns her skis so they point a bit off to the side rather than straight down the slope the skis tend to skid sideways and skis moving sideways offer much more resistance to the snow. The effect of this is a new force on the skier directed toward the side to which the skis were turned. In accordance with the second law, this force causes an velocity component off to the side, changing the direction of the skier's path.

The third law says that all forces involve two objects and the force acts with equal strength but opposite directions on each. The two objects are the skier and the snow in the case of the turning skier. The force on the skier changes her path and the force on the snow throws up a spray of the white stuff in a direction opposite the turn.