3Biomechanics is a very useful science in the study of human performance especially in the area of perfecting technique.Biomechanics forces may be eithera) static – which is concerned with bodies at rest, orb) dynamic – which is concerned with forces producing movement
4MOTIONTRANSLATORY – 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 linesCurvilinear – 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 bodyExternal Axis – the whole body travels around an axis that is outside the body
5GENERAL MOTIONMost 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.
6PROJECTILE 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. tennisProjecting the body itself – eg. High jump
7The TRAJECTORY (path of a projectile) is influenced by two sets of factors Propelling factors (ie factors at its release)Speed of releaseHeight of releaseAngle of releaseFactors in the airGravityAir resistanceSpinAerodynamics
8Effects of Air Resistance and Aerodynamics A - No air ResistanceB – Air resistance
9We can draw some conclusions We can draw some conclusionsSpeed of release - The greater the speed of release, the greater the horizontal distanceHeight of release – the greater the height of release, the greater the horizontal distanceAngle 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?
10What happens when we have different angle of release?
11Angle of release look at the requirements for different activities ActivityTennis ServeVolleyball float serveLong jumpDiscusHigh jumpStanding back somersaultAngle (degrees)-3 to 1513 to 2017 to 2235 to 3940 to 5075
12What are the different objectives for our projectiles 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 vaultMaximum possible speed of releaseMaximum possible angle of releaseDistance eg discus, long jumpCorrect angle of release for activityApplication of spin in some casesSpeed eg rugby passLowest possible angle of releaseAccuracy eg archery, netball
14Biomechanics 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 partsThe Fulcrum or Pivot point - The point about which the lever worksLoad or Resistance - The force being overcome by the lever systemEffort or Force - The force being applied to overcome the loadThere are three classes of levers -1. First class - See-saw and Crowbar2. Second class - Wheelbarrow3. Third class - The boom of a crane
151st Class LeverThe fulcrum lies between the effort and the load
162nd Class LeversThe fulcrum lies at one end of the lever arm with the Effort being applied at the other end
173rd Class LeverThe fulcrum lies at one end of the lever arm with the effort being applied between it and the load
19INERTIA Inertia is a bodies resistance to change in motion. Inertia is described in Newton’s First Law“A body continues in it’s state of motion or rest unless acted on by a force”Inertia is related to mass well as shape and friction
20Inertia in ActionInertia 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
22NEWTON’S THIRD LAWNewton’s 3rd law relates to Action / Reaction“For each and every action, there is an equal and opposite reaction”
23FORCE SUMMATIONThe velocity of a projectile depends on the speed of the last part of the body at the time of contact or release
24FORCE SUMMATIONIf 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
25TIMING 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 / speedEg. In a well-timed Volleyball spike; the forearm begins to extend at the elbow just as the upper arm begins to deccelerate