KEY KNOWLEDGEKEY SKILLS Projectile motion of the human body and objects through the air and through water  Key principles associated with projectile motionof objects including lift, the Magnus effect, spin, height and angle of release, velocity of release, angle of projection and flight path.  Correct use of terminology to explain how biomechanical principles apply to a range of sports actions  Describe how spin can be used to bring about successful performances in sport such as swing, lift and turn  Participate in, analyse and report on a range of practical activities that consider biomechanical principles  Use biomechanical principles to critique the effectiveness of different movements  Analyse different sporting actions to identify similarities and differences as well as the correct application of biomechanical principles to improve performance © Cengage Learning Australia 2011

Anything launched into the air (only influenced by gravity and air resistance) has a projectile motion. Projectiles have both a vertical and horizontal component. The vertical component is influenced by gravity and force of projection. Projectile motion The horizontal component is influenced by air resistance © Cengage Learning Australia 2011

angle of projection / release speed of projection / release height of projection / release. Factors affecting flight path of a projectile © Cengage Learning Australia 2011

This is the angle at which an object is released into the air. Angle of projection © Cengage Learning Australia 2011

This is influenced by the vertical component which determines the height reached and the flight time of an object, and the horizontal component / force, which determines the horizontal distance covered by the object. Speed of release © Cengage Learning Australia 2011

This is calculated by subtracting the height that the projectile is released, from the height at which it stops/ ends. If height of release is 0° (projection height and landing height are both equal) optimal angle of release = 45°. If height of release is greater than 0° (projection height is above landing height) optimal angle of release = less than 45°. If height of release is less than 0° (projection height is below landing height) optimal angle of release = greater than 45°. Height of release © Cengage Learning Australia 2011

Laminar and turbulent flow When objects move through air or water slowly they do not disturb the flow a great deal and the air or water will flow in a smooth, parallel manner around the object = laminar flow. Human movement through air and water When objects move through air or water rapidly they disturb the flow to the point that layers next to the surface of the object get mixed together = turbulent flow © Cengage Learning Australia 2011

This is upwards force acting on a body within water. The buoyant force = weight of fluid displaced by an object. The greater density a fluid has, the more buoyant objects will be when placed in this medium. When buoyancy force and weight are equal and object will float, but when weight of an object is greater than the buoyancy force, it will sink. Buoyancy © Cengage Learning Australia 2011

Is created when an object moves through a fluid or when fluid flows around a stationary object. In air the drag force is known as air resistance In water the drag force is known as hydrodynamic resistance Drag force Forces will always act from the area of high pressure to an area of low pressure. Streamlining decreases turbulence created at the back of an object and thus reduces drag. Bernoulli’s Principle explains how as the velocity of fluid increases, the pressure decreases. This causes an area of turbulence behind the object where pressure is less than in front of the object. © Cengage Learning Australia 2011

Drag is affected by the following factors: the shape of an object and how streamlined it is the density of the fluid (air or water) the velocity of the object as it moves through the fluid the cross sectional area of the object in the direction of the motion. © Cengage Learning Australia 2011

Lift force acts perpendicular to the flow of the fluid and is affected by: A foil has a curved and a flat surface which causes fluid to flow faster over the curved surface than the flat one, leading to pressure differences. Lift force is generated from the area of high pressure to the area of low pressure. the velocity of the fluid the density of the fluid the size, shape and position of the object the foil shape angle of object relative to direction of flow the Magnus effect uneven surface coatings. © Cengage Learning Australia 2011

This is the angle between the long axis of the object and the direction of air / water flow. A positive angle of attack is required to create lift force Angle of attack © Cengage Learning Australia 2011

Lift can be created by spin (topspin, backspin and sidespin) and the deviation towards the direction of spin is knows as the Magnus effect. A lift force will act from the area of high pressure to the area of low pressure. The Magnus effect © Cengage Learning Australia 2011

Air will travel across a smooth surface quicker than over a rough surface. Turbulent air from the rough surface is at lower pressure than air flowing over the smoother surface which is at higher pressures. This causes a pressure difference, and lift force is towards the side with lower pressure. Surface differences © Cengage Learning Australia 2011