1.3.a. Biomechanical principles, levers and technology Typeit

Friction and air resistance

The measure of an object's resistance can be determined by both friction and air resistance. The two terms differ in that friction occurs from the interaction between two surfaces, whereas air resistance is the interaction between an object's surface and the air. They both act to impair the  of movement and can be affected by various different factors:

• Velocity – The greater the velocity, the  the air resistance. This can be applied in practice during everyday activity. Take a still day, for example; the wind is likely to go unnoticed when walking at a slow pace, but if walking were to turn into a jog, it might seem that the wind had picked up. In fact, this is simply a reflection of the relationship between velocity and air resistance.
• Surface properties – It is important that surfaces are  if a performer wants to the limit the effect of air resistance. An example of this is the adoption of Lycra clothing in sports performed at high speeds, such as cycling and sprinting. If the surface were rough, this would impair the speed of movement by increasing air resistance. The same applies for friction – passing along the ground in football can be used as an example where if the same force were applied to the same ball it would have less friction, and thus travel , on a smooth surface such as an indoor gymnasium floor than on the rough surface of an outdoor grass pitch. There are many cases in sport where a performer would seek to increase friction between themselves and the ground to benefit sports performance. This can be demonstrated by the track athlete who wears running spikes to increase grip when running around bends, as well as the Formula One driver who performs a warm up lap of the track before a race, as an increase in  increases friction between the racing car and the track, maximising traction when turning tight corners at high speeds.
•  – An object with a flat surface is said to be 'aerodynamic', reducing the air resistance that impairs its speed of movement. For example, the streamlined design of a Formula One car and the placement of the driver allow for the smooth passage of air, thus maximising the speed at which the car travels.
• Front cross-sectional area – The smaller the front cross-sectional area of an object, the  effect air resistance has on it. For example, the small front cross-sectional area of the javelin allows it to travel further than the object in any other field athletics throwing event.