Biomech noteskoodle

Y12 Physical Education AS90433

Bio mechanics

Biomechanics studies what makes a body move. It studies internal and external forces (remember a force is a push or a pull) that act on the body and other objects. It is possible to work out how your body should move in order to perform a task more efficiently. So for example we can use biomechanics to make you a better player!


Biomechanics Summary

Balance and StabilityNewton's LawsForce SummationProjectile MotionLevers


Balance and Stability

This is defined as the ability to hold or maintain a position in space

Stability generally depends on:The location of the centre of

gravity (COG) with respect to the base of support.

The direction of forces involved



Centre of Gravity is the point in the body at which all body parts are in balance.

In the anatomical position males generally have a higher COG than woman.

The body rotates around the COG


Four Main Principles of Stability

1. The closer the line of gravity is to the centre of the base of support, the greater the probability of maintaining balance

2. The broader the base of support, the greater the probability of maintaining balance.


Four Main Principles of Stability

3. Our balance is improved when we lower our Centre of Gravity in relation to the base of support. eg:

4. The further one part of the body moves away from the line of gravity, the probability of maintaining balance decreases unless another body part moves to compensate for it. eg.



We can further increase stability:

Increase Friction eg________Lean into an incoming Force eg______Increase Rotation eg________Increase Mass eg________


Newton’s Laws of Motion

Newton’s First Law: Law of InertiaAn object at rest tends to remain at rest

unless it is acted on by an external force.An object in motion tends to remain in

motion and to travel in a straight line with uniform velocity unless acted on by an external force.



Newton’s Second Law: Law of Acceleration

When a force acts on a body, it’s resulting change in momentum is proportional to the force causing it and inversely proportional to the mass

Force = Mass x Acceleration



Newton’s Third Law: Law of Action/Reaction

For every action there is an equal and opposite reaction


Force Summation

To give an object momentum eg throwing, kicking, hitting, the amount of momentum given to the object is determined by the ‘sum of all forces generated by each body part’.


Force Summation

Five Basic Guidelines to generate optimal force:Use of body segments Stretch outSequencing of Body segments – larger firstTiming of Body SegmentsFull Range of Motion

See Handout


Force Summation

Note importance of:StabilisationTiming


Force Summation

Consider force summation in relation to drawing and driving.


Projectile Motion

Any object released into the air is a projectile. eg?

Six Factors Affect a Projectile’s PathGravityAir resistanceSpeed of ReleaseAngle of ReleaseHeight of ReleaseSpin


Projectile Motion

Of the six, the most important factors are Gravity which acts to decrease the height a projectile will travel and Air Resistance which acts to decrease distance.

Note a projectile will travel in a parabolic curve unless acted on by another influence


Gravity and Air ResistanceGravityEffects an object at a constant of 10NGravity is a weak attractive force but we

cannot escape it!

Air Resistance Effects the path of a projectile depending

on its mass, speed and/or surface area. Eg Graph the path of a petanque ball vs a shuttlecock


The greater the speed of release, the greater the distance traveled.

Two Parts:Initial Vertical SpeedInitial Horizontal SpeedThe greater the vertical speed: the higher and

longer (time) the projectile will fly.The greater the horizontal speed: the further it

will fly.

Speed of Release


Speed of Release

Force = Mass x Acceleration

To increase force can increase one or both. How?

This may create problems such as …

Remember Newton’s Second Law:


Angle of Release

You need an optimum angle to maximise the benefits of vertical and horizontal velocity.

If the angle is too high:

If the angle is too low:


Angle of Release•Angling of the release of the bowl allows for what to occur?


Height of Release

As the Height of Release increases, so does the distance that will be gained.

Not really relevant in bowls but definitely in Petanque – How?


Spin

In order to cause rotation a force has to be applied to one side of the COG.

Topspin Causes:

Backspin Causes:


Levers

Levers consist of 3 parts1. Resistance2. Effort3. Fulcrum or Pivot

1 2

3


Levers

Two main functions:

To increase the resistance that can be moved eg__________

To increase the velocity at which an object will move with a given force. eg _______

There are 3 types of levers. See handout.

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