Explain Forces and motion.

The coefficient can also be increased by increasing the force that presses the surfaces together; mountain bikers often sit back over the driving wheel when riding up a muddy slope in order to gain a better grip of the tyre on the surface. Friction forces can also be increased by increasing the surface area in contact with another, e.g. an athlete wearing spikes on a tartan track.

Fluid forces

Fluid forces are caused by air and water, when an object moves through water or air it is affected by fluid friction which acts in the opposite direction of the moving body. the amount of air resistance of fluid friction experienced depends upon the shape of the object and the speed at which the object is moving.

Air resistance affects most sporting activities, although its affects on performance differ. Air resistance can affect the performer in flight e.g. long jump, Projectiles such as balls, shuttle cocks and javelins, Cyclists and Sprinters.

Air resistance on a projectile while in flight may change the parabolic flight path. These are the expected flight paths on different projectiles:

Flight paths can be categorised as:

• Parabolic (a uniform symmetrical shape)
• Nearly parabolic
• Asymmetrical

Faster moving objects have greater air resistance. This causes rapid deceleration and slowing down of the projectile until a point is reached where weight becomes the determining factor, leading to an asymmetric flight path.

Fluid resistance

The fluid resistance is shown by the forces acting upon the swimmer.

The drag force is dependant upon four main factors:

1. The forward cross section of the swimmer. The reduce drag, the swimmer should adopt a streamlined position; maintain a flat position close to the surface, without dropping the feet.
2. The surface area in contact with the water. This concerns the swimmers body shape.
3. Surface effects. Swimmers attempt to minimalise turbulent flow by wearing shiny swimsuits, wearing swimming hats and shaving down. This allows the water to flow past the body more smoothly and limit the drag force.
4. Speed of the swimmer. The relationship between speed and drag is positive – the faster you swim, the greater the drag. In competitive swimming the swimmers have to swim as fast as they can so there is little they can do to prevent the increased drag so they have to adopt an efficient technique that minimises drag yet enables fast swimming.

Gravity

Gravity is an external force that naturally occurs and pulls a body or object towards the centre of the earth. Newton’s law of gravitation states:

All particles attract one another with a force proportional to the product of their masses, and inversely proportional to the square of the distance between them.

Due to the immense difference between the mass of the earth and object involved in sporting activity, the gravitational force of attraction between the two bodies is large, and has a significant effect upon performance.