# BIOMECHANICS - macphysed

BIOMECHANICS Biomechanics is the study of the internal and external forces which act on the body, and the effects produced by those forces. Biomechanics is a very useful science in the study of human performance especially in the area of perfecting technique.

Biomechanics forces may be either a) static which is concerned with bodies at rest, or b) dynamic which is concerned with forces producing movement MOTION TRANSLATORY this is when all parts of the body follow parallel lines. There are two types: Linear all parts of the body move in straight parallel lines

Curvilinear all parts of the body move in curved parallel lines. ANGULAR, or ROTARY This when a body moves about an axis. There are two types: Internal Axis the axis is within the body External Axis the whole body travels around an axis that is outside the body GENERAL MOTION Most motion is in fact a combination of both

angular and linear and we describe this as GENERAL motion. For example a cyclist has angular motion with the wheels, the pedals, and his limbs, but the bike frame and his trunk experiences linear motion. PROJECTILE

MOTION What is a projectile? Any body released into the air is a projectile. This means that once it is in the air it has no extra propulsion. A body can be released into the air by either Throwing eg. Discus, Striking eg. tennis Projecting the body itself eg. High jump The TRAJECTORY

(path of a projectile) is influenced by two sets of factors Propelling factors (ie factors at its release) Speed of release Height of release Angle of release Factors in the air

Gravity Air resistance Spin Aerodynamics Effects of Air Resistance and Aerodynamics A - No air Resistance B Air resistance http://www.walter-fendt.de/ph11e/projectile

.htm We can draw some conclusions Speed of release - The greater the speed of release, the greater the horizontal distance Height of release the greater the height of release, the greater the horizontal distance Angle of release There is an optimum angle of release for each object, but that will depend on a number of factors including aerodynamics of the object and height of release eg. In

Volleyball, what advantage is there in a jump serve? What happens when we have different angle of release?

Angle of release look at the requirements for different activities Activity Angle (degrees) Tennis Serve -3 to 15 Volleyball float serve 13 to 20 Long jump 17 to 22 Discus

35 to 39 High jump 40 to 50 Standing back 75 somersault What are the different objectives for our projectiles? And, what do we need to do to maximise our chances of success?

Height eg high jump, pole vault Maximum possible speed of release Maximum possible angle of release Distance eg discus, long jump Maximum possible speed of release Correct angle of release for activity Application of spin in some cases Speed eg rugby pass Maximum possible speed of release Lowest possible angle of release

Accuracy eg archery, netball LEVERS Biomechanics and Levers A lever is a mechanism made up of a lever arm (with 2 forces acting on it) and a pivot point. It has three parts The Fulcrum or Pivot point - The point about which the lever works Load or Resistance - The force being overcome by the lever system

Effort or Force - The force being applied to overcome the load There are three classes of levers 1. First class - See-saw and Crowbar 2. Second class - Wheelbarrow 3. Third class - The boom of a crane 1 Class Lever st

The fulcrum lies between the effort and the load 2nd Class Levers The fulcrum lies at one end of the lever arm with

the Effort being applied at the other end 3rd Class Lever The fulcrum lies at one end of the lever arm with the effort

being applied between it and the load 3 classes of levers INERTIA Inertia is a bodies resistance to change in motion. Inertia is described in Newtons First Law A body continues in its state of motion or rest

unless acted on by a force Inertia is related to mass well as shape and friction http://www.physicsclassroom.com/Class/newtla ws/U2L1b.html Inertia in Action Inertia is easily observed if you think about being in a vehicle. When it brakes hard, you are thrown forward. This is because you have your own moving inertia. When

the vehicle alters its own inertia you still continue with yours until a force works on you NEWTONS THIRD LAW http://www.physicsclassroom.com/Class/newtla ws/U2L4b.html Newtons 3rd law relates to Action / Reaction For each and every action, there is an equal and opposite reaction

FORCE SUMMATION The velocity of a projectile depends on the speed of the last part of the body at the time of contact or release FORCE SUMMATION

If you wish to achieve maximum velocity, it is important that each body part is used in the correct sequence. You use the strongest, heaviest muscles first, before using the smaller, faster muscles last. This overcomes inertia

TIMING The timing of the application of the forces is vital A body part should begin to move when the previous body part is exerting maximum force / speed Eg. In a well-timed Volleyball spike; the forearm begins to extend at the

elbow just as the upper arm begins to deccelerate

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