biomechanics

linear momentum definition

the product of an objects mass multipled by its velocity

linear momentum formula

P=MxV where p=linear momentum, m=mass, v=velocity.

impulse definition

the change in momentum. it is also equal to the product of force and the time interval during which the force acts.

impulse formula

impulse= force x time

Force production definition:

Amount of forces given to an object

force absorption:

amount of time for absorption given to catch a ball.

• increased time of absorbing peak force=less force/more force absorbed.

• decrease time of absorbing peak force. = more force/more force absorbed.

coefficient of restitution definition

a value respresenting the ratio of the velocity after an impact compared to the velocity before impact: (bounciness of an object).

coefficient of restitution formula

CoR= square root of bounce height over drop height. … alway between 0 and 1

CoR=1

• PERFECT ELASTIC COLLISION

• all energy that existed remains after the bounce.

• all linear momentum is conserved.

CoR=<1&>0

• PARTIALLY INELASTIC COLLUSION

• some energy is lost to the bounce.

• most collision are in this category.

• energy is lost due to change of shape, heat and sound.

CoR =0

• PERFECTLY INELASTIC COLLISION:

• no energy remains after the bounce.

equipment of interacting bodies

• newer materials will often have higher CoR than older.

• more elastic materials will have higher CoR.

• Often the CoR at competitions is regulated.

velocity of the collision

• higher velocity will reduce CoR due to greater compression and therefore greater change of shape.

• this is velocity of ball and the implement that may be used to hit the ball.

temperature of materials:

• as temp increases, so does the CoR.

• often as an object heats up it becomes more bouncy.

moment of inertia definition

a bodys tendency to resist angular motion.

moment of inertia formula

moment of intertia= sum x mass x r²

angular momentum- definition

the quantity of rotation of a body.

angular momentum - formula

angular momentum(L)= (W) angular velocity x (I) moment of inertia.

Third class lever system

lever system where the force is between the resistance and the fulcrum.

• speed multiplier, promotes speed at the end point of the lever.

• often attempt to increase over all length of lever to maximise this speed at end point.

balance:

refers to the body’s or an objects ability to maintain equilibrium when stationary (static) or moving (dynamic)

base of support:

area bounded by the outermost region of contact between a body and support surface.

centre of gravity:

the theoretical point in an object where all of the body’s mass is equally distributed.

line of gravity:

imaginary vertical line passing downwards through the centre of gravity to the ground or surface the person is on.

Mass

amount of matter in an object/resistance to a change in position.

simultaneous:

use of multiple body parts at the same time to produce a force.

sequential:

activation of body parts used in a sequence to produce a force.

angle of release:

the angle at which an object is released.

projectile motion: factors

1. angle of release

2. velocity of release

3. height of release

velocity of release:

the velocity of the projectile when it is released.

height of release

the height from the ground that the projectile is released at.

optimal projection:

is the relationship between the angle velocity, and height of release/ landing to attain the goal of the athlete.

questions for optimal projections:

1. what is the aim of the activity?

2. is the release height the same as landing height?

third class lever

where the force lies between fulcrum and resistance. the length of the resistance arm when shortens allows easier movement to lift objects.

general principles for optimal angle:

release height = landing height =45 (kicking soccer ball from ground)

release height > landing height<45 (throwing)

release height < landing height >45 (hitting golf ball onto elevated green)

fluid

air and water

fluid resistance

as an object moves through a fluid it disturbs that fluid, it transfers energy to the fluid.

boundary layer.

thin layer of air surrounding or attached to an object as it moves through the air.

boundary layer separation

where the boundary layer breaks away from the object.

laminar flow

type of flow in which the fluid travels smoothly or in regular paths.

turbulent flow

type of flow in which the fluid undergoes irregular fluctuations or moving.

drag definition

a force that resists the motion of objects through a fluid .

types of drag

1. surface drag

2. form drag

3. wave drag.

surface drag definition.

friction produced between fluid and the surface of moving object.

surface drags and factors effecting it:

1. roughness of the surface- rougher surface= more drag

2. viscosity of the fluid - increase viscosity =more drag

3. surface area - larger surface =more drag.

4. velocity of the object - higher velocity =more drag.

form drag:

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

• if there is a matter pressure differential there will be less drag.

form drag: factors affecting it:

1. cross sectional area - increase cross sectional area =more drag.

2. shape of the object- streamlined shaped = less drag.

3. roughness of the surface = rougher surface = less drag.

4. velocity of the object = higher velocity = more drag.

wave drag definition:

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

wave drag considerations:

1. techniques

2. under water vs above.

3. open vs closed conditions.

bernoulli’s principle:

an increase in the velocity of a fluid occurs simultaneously with a decrease in pressure.