Biomechanical principles of motion through air and water.

(chapter 5) By Georgia and Cade

Key knowledge

• Projectile motion (including the human body as a projectile), Magnus effect, spin (back spin, top spin, side spin), height of release, angle of release, velocity of release, angle of projection and flight path (trajectory).

• In human movement , the two mediums that we generally perform in are air and water.

• • • • Air and water both effect the motion of an object as it moves.

Water and air, like all gases and liquids, are fluids, so both exert forces on the body or an object as it moves Because of this, it is much harder to ride into a head wind than it is to ride with a tail wind, swimming out from a beach in a ocean is much harder than returning to shore.

Therefore, cyclists, downhill skiers, swimmers and runners try to streamline their bodies as much as possible.

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Projectile motion

Anything that is launched into the air and affected by forces of gravity and air resistance can be considered a projectile. In sport and physical activity, the human body is often a projectile.

In athletics, diving and gymnastics, athletes can be required to project themselves into the air

Vertical and horizontal components

• Anything launched into the air that can be considered a projectile will have horizontal and vertical components.

• • • • Factors affecting the path of a projectile: -angle of projection (or release) -speed of release (or projection) -height of release (or projection) • • The angle of projection is the angle at which an object is released into the air. There are three shapes a flight path can form, depending on the angle od release: vertical shape (straight up and down), parabolic (when projectile is between 0-90 degrees), parabola (object projected at 0 degrees or perfectly horizontal).

Human movement through air and water

• Laminar and turbulent flow.

When an object moves through a fluid medium (air or water) the air or water will flow in smooth, parallel layers around the object, this is called laminar flow.

Magnus effect

• • • Lift can be generated by spinning objects. A spinning object increases the speed of fluid on one side and decreases it on the other. This will create regions of high and low pressure on either side of the object, generating lift.

This pressure creates a Magnus force, which is a lift force that will act from the area of high pressure to the area of low pressure, causing the object to deviate in the direction of the spin. This deviation is known as the Magnus Effect