pe studies - biomechanics

biomechanics

the study of motion and the effects of forces relative to the body, applies to the laws of mechanics and physics to human performance which contributes to the improvement in mechanical aspects of sports performance

benefits of biomehanics

technique efficiency, injury reduction, modification of sports equipment and technological development of equipment and computer technology

momentum - definition

a measure of the amount of motion possessed by a moving body (mass x velocity = momentum)

impulse - definition

the application of force over a period of time to change the momentum of an object (force x time = impulse)

momentum - key concepts

an object can only have momentum if it is moving, the greater momentum more force needs to be applied to either stop or slow the object and as a result when two bodies collide, the one with the most momentum will be least affected

impulse - key concepts

it creates momentum, changes momentum and stops momentum

increasing momentum

one must aim to increase force through effective summation of force and improved strength and time component through technique and equipment modifications

CoR: coefficient of restitution - definition

measures the elasticity of the collision between an object and a given surface

coefficient of restitution - key concepts

it measures how much energy remains in the object after a collision occurs and elasticity is a measure of how much rebound exists following a collision

measuring CoR - 1

CoR of 1 represents a perfectly elastic collision eg. when a ball is dropped from a given height, the ball will rebound to that same height after colliding with the ground

measuring CoR - 0

CoR of 0 represents a perfectly inelastic collision, effectively stopping at the surface which is collides with eg. when a ball is dropped it doesn’t bounce at all

factors affecting CoR

equipment and surfaces, temperature of the balls and velocity of the collision

factors affecting CoR - equipment and surfaces

conditions of the balls eg. new tennis balls have a higher CoR compared to old ones, type of equipment eg. aluminum bats have a higher CoR compared to wooden bats and type/condition of playing surface eg. clay courts have a higher CoR compared to grass courts

factors affecting CoR - temperature of the ball

increased temperature results in an increase in CoR eg. warm squash balls have increased bounciness compared to cold ones

factors affecting CoR - velocity of the collision

velocity between the oncoming ball and swinging implement will alter the CoR and increasing the velocity increases the likelihood of the ball losing energy due to greater compression of the ball

angular motion - definition

refers to the quantity of angular motion possessed by a rotating body

moment of inertia - definition

refers to the resistance of a rotating object to change its state of motion

angular velocity - definition

refers to the rate of change in angular position of a body

linear sense

mass x velocity = linear momentum

angular sense

moment of inertia x angular velocity = angular momentum

moment of inertia - key concepts

if the mass of an object is distributed close to the axis of rotation, the moment of inertia is small and it is easier to rotate the object vice versa

radius of rotation

how the objects mass is distributed about the axis of rotation

angular momentum example - sit up

doing a sit up with a medicine ball above your head is harder due to the mass is further away from the rotation which is the hips but it is easier when the medicine ball is at your chest

conservation of angular momentum

indicates a rotating body will continue to rotate indefinitely unless a external force acts on it

three parts of levers

resistance arm, axis and force arm

resistance arm

the distance between the fulcrum and the center of the resistance

axis/fulcrum

the point around which the lever rotates

force/effect arm

the distance between the fulcrum and the point at which the force is applied

input force

force exerted on the lever

output force

force exerted by the lever

third class level

the axis is located at one end, with the application of the force in the middle and resistance applied at the opposite end - muscle attachment represents the application of force, the joint represents the axis and the weight represents the resistance

balance

the ability to neutralise forces that disturb equilibrium OR the ability of something to maintain or hold its position

factors affecting balance

size of base of support, height of center of gravity, line of gravity and mass of the object

factors affecting balance - size of base of support

the greater the base of support, the more balanced you will be

factors affecting balance - height of center of gravity

the lower the height of center of gravity the more balanced you will be

factors affecting balance - line of gravity

the closer the line of gravity is to the middle of the base of support, the more balance you will be

factors affecting balance - mass of the object

the greater the mass, the more balanced you will be

segmental interaction

forces acting between the segments of a body can transfer energy between segments OR how the body segments interact to meet the tasks demands

two factors affecting segmental interactions demands

power: more segments used, forces usually sequentially summated eg. softball hit and accuracy: less segments needed, forces usually simultaneously summated eg. netball goal shot

two force summations

simultaneously and sequentially summation

simultaneously summation

where all body parts move at the same time to produce force and produces accuracy eg. putt in golf

sequentially summation

forces produced by different parts of the body acting together to maximise force eg. baseball pitcher

principles to sequentially produce maximal force effectively

begin movement with larger and stronger muscles, transfer momentum progressively through the body, maintain stability in each body part to support momentum transfer, involve multiple body parts to sustain force over time, follow through to manage deceleration safely and direct all forces toward the intended target

optimal projection

the relationship between the angle, velocity and height of release/landing height to attain the athletes goal

angle of release

with all other factors equal, throwing at an angle of 40-43 degrees to maxmise distance

fluid mechanics

the natural science of fluids in motion - liquids or gases

fluid mechanics - key concepts

fluid forces have little effect on an objects motion like shot put or a large effect on an objects motion like swimming

boundary layer

a think layer of air surrounding or attached to the ball either laminar or turbulent

boundary layer separation

where the boundary layer breaks away from the ball and the earlier this happens the greater the pressure gradient between the front and back of the ball leading to increased drag

laminar flow

a type of fluid flow in which fluid moves smoothly in individual layers or streams

turbulent flow

flow in which the velocity at any point varies erratically

factors affecting boundary layer separation point

velocity, surface roughness and shape

factors affecting boundary layer separation point - velocity

low velocity causes the boundary layer to cling to the surface separating well towards the rear with minor drag and high velocity causes separation to occur further forward with increased drag

factors affecting boundary layer separation point - surface roughness

rough surfaces create turbulent boundary layer reducing the effect of drag eg. swimsuits designs are now rough surfaces to create a turbulent boundary layer resulting in late separation

factors affecting boundary layer separation point - shape

oval ball causes the boundary layer to cling to the surface separating well towards the rear with minor drag and round ball causes separation to occur further forward with increased drag

types of drags

pressure, surface and wave drag

surface drag - definition

friction produced between fluid and the surface of a moving object

factors affecting surface drag

velocity of a moving object, roughness of a surface object, viscosity of the fluid and surface area

pressure drag - definition

resistance created by the pressure differential between the front and back of an object moving through a fluid

factors affecting pressure drag

cross-sectional area of the object presented to the fluid, velocity of the object, surface roughness and shape of the object

wave drag - definition

resistance formed by creation of waves at point where air and water interact

factors affecting wave drag

velocity of the wave, technique and conditions

factors affecting drag

drag coefficient, mass, velocity, surface roughness, cross sectional area and shape

factors affecting drag - drag coefficient

measure used to quantify the drag or resistance of an object in a fluid environment and directly related to cross sectional area

factors affecting drag - mass

the greater the mass of the ball the less effect of drag

factors affecting drag - velocity

the faster the ball moves through the air the earlier the boundary layer separates from the ball creating a large pressure differential between the front and rear of the ball hence more drag

factors affecting drag - surface roughness

rougher surfaces allow for the air stream to cling to the ball for longer periods resulting in a smaller pressure differential between the front and rear of the ball hence less drag

factors affecting drag - cross sectional area

a linear relationship exists between cross sectional area exposed to air and drag causing an increase in CSA means an increase in drag