Biomechanics VCE P.E
SUMMATION OF MOMENTUM • Summation of momentum is the sequential movement of body parts to produce maximum force and speed. This is achieved through moving the slowest and largest (therefore the most momentum) body parts first. As smaller body parts are included in the action, the force developed is transferred to them from the larger body parts. • It is important that an effective follow through is employed to ensure the force that has been developed is not lost in deceleration prior to ball release/contact.
The size and mass of the object to be hit/swung/thrown is also a factor, heavier objects will affect the summation of force (medicine ball v tennis ball). Gross and fine motor skills also affect the summation of force, fine motor skills will not require whole body force summation (javelin v darts).
ACCURACY • Accuracy is a precise and controlled movement at the appropriate time that brings about an exact or desired outcome. Accuracy is determined by the direction of the force and the amount of force applied. Accuracy is simply hitting the target.
PROJECTILE MOTION • Projectile motion looks at the factors that affect an airborne object. It is when an object is projected into the air with some horizontal velocity and is acted upon by gravity.
TRAJECTORY OF A PROJECTILE • A projectile will always follow a parabolic flight path as it is constantly being accelerated by gravity. The flight path will always be affected by the following factors: • Velocity of release: increasing the velocity at release can increase the height of the flight path, the length of time in the air and the distance it travels. • The angle of release: If spin or air resistance are not taken into account and height of release is zero, there are three alternatives for flight path: • 45˚ will result in the greatest horizontal distance the ball can achieve • >45˚ will result in shorter distance, greater height and flight time • <45˚ will result in shorter distance, lower height, shorter flight time. • The height of release: Increasing the height of release in general will increase the flight times and distance travelled (if angle of release and velocity are constant)
FACTORS WHICH AFFECT THE PATH OF PROJECTILE MOTION • AIR RESISTANCE • Increases in air resistance will decrease flight time and distance covered. Air resistance is friction between the projectile and the air surrounding. The greater the surface area, the greater the effect of air resistance. • SPIN • The magnus effect describes the path taken by a spinning projectile. The magnus effect details the relationship that causes a spinning object to turn toward the spinning direction. There are three types of spin that can be imparted on the ball: backspin, topspin or sidespin.