PE AOS 4

Biomechanics

the study of human movement form mechanical perspective 

some types of medical tools in biomechanics

• Goniometry is used to measure join angles  

• Electromyography records the electrical activity within a muscle joint prior to contraction  

• Accelerometers measure the bodies first acceleration  

kinetics 

the study of forces and their effects on motion in the body. force, mass, inertias 

kinematics 

the description of motion. distance, displacement, velocity 

4 categories of biomechanics

• Force- push of pull acting on the body or an object  

• Motion- when an object, body or body part is moving. Many different types including linear, angular  

• Stability and balance- the ability to resist against forces 

• Levers- consists of rigid bar (golf club) that rotates around an axis to generate force 

Force

a push or pull acting on body or an object upon interaction with another object  

friction 

when 2 surfaces go against each other e.g chalk on hands for gymnastics 

gravitational force

the force of attraction between two bodies or objects. 

weight

the force exerted on the body by gravity

= Mass x gravity  

drag

When an object or body move through water or air it experiences a force causing a body or object to slow down

factors that affect drag

• The surface area of the object 

• Density and kind of fluid  

• speed of object

inertia

the tendency for a body or object to resist a change in its state of motion  

Momentum 

a measure of the amount of motion an object has and its resistance to changing that motion  

conservation momentum

The total momentum before collision is the total momentum after collision as the momentum. not lost, transfers

summation of momentum

correct timing, sequence, large slow muscle groups first followed by small fast muscle groups

impulse

the equal to change in momentum of an object

 =time x force

impulse reducing injuries 

An object needs to be brought to rest from a certain first velocity = change in momentum. (for example – catching a cricket ball) 

newtons first law

a body will remain at rest or in uniform motion in a straight line unless acted upon by an external force 

newtons second law

force applied to an object will produce a change in motion (acceleration) in the direction of the applied force that is directly proportional to the size of the force  

newtons third law

for every action there is an equal and opposite reaction  

levers

The musculoskeletal system is functioning as a series of levers  The skeletal and muscular systems work together to produce movement in the body. 

third action lever

a lever where force is between the resistance and the axis designed for speed and range of motion

Mechanical advantage 

Refers to the ability of a lever system to move a large load with a small amount of effort, making physical tasks easier  

mechanical advantage formula

force arm

over

resistance arm  

when at a mechanical advantage ( = < 1)

force arm is greater than the resistance arm and the velocity is decreased but the force is increased

when at mechanical disadvantage ( = > 1)

force arm is less than the resistance arm and the velocity is increased but the force decreased

how to increase VS decrease friction

increase: apply chalk to hands to grip bar

decrease: applying lubricant to bat