The weight of a person skiing affects the amount of friction between the person and the snow. The weight of the skier also affects how much force is needed to accelerate the skier. Linear acceleration manifests itself as an increase in velocity (speed), while rotational acceleration manifests itself as a change in direction.
Static Friction
Friction is the resistance level between two surfaces sliding past one another. In general, rougher surfaces produce more friction. There are two types of friction: static and kinetic. Static friction describes the amount of friction between two objects before one or both of them start to move. It can be thought of as the initial resistance that must be overcome in order to produce motion. Static friction increases with the weight of the sliding object or person. As a result, heavier skiers must use more force to begin moving.
Kinetic Friction
Kinetic friction describes the amount of friction between two objects after one or both of them start to move. It can be thought of as the continual resistance that must be overcome in order to maintain motion at a given velocity. Kinetic friction varies directly with the weight of the sliding object or person. As a result, a heavier skier must use more force to maintain his speed in a race.
Acceleration
Acceleration is defined as the change in velocity of a moving object or person. In this case, the moving person is the skier. The amount of force needed to accelerate the skier is equal to the amount of acceleration multiplied by the mass of the skier. Mass varies directly with the weight of the skier, as mass is simply weight divided by gravity. As a result, a heavier skier must use more force to accelerate himself in a race.
Changing Direction
While the term "acceleration" usually refers to linear acceleration, it also encompasses rotational acceleration, which manifests itself as a change in direction. For example, if you swing a ball on a string above your head, the ball moves in a circular path because of the rotational acceleration imparted by the force of your hand and the ball's attachment to the string. The amount of force needed for rotational acceleration varies directly with the weight of the skier. As a result, a heavier skier must use more force to change direction in a race.
References
- "Kaplan SAT Subject Test: Physics"; Hugh Henderson; 2011
- Georgia State University; Force; R. Nave; 2011
Member Comments