1.3 - Biomechanics Flashcards
what is linear motion
the movement of a body in a straight or curved line, where all body part move the same distance, in the same direction, over the same time
how is linear motion created
direct force applied through a bodys centre of mass
what does the gradient on a speed time graph represent
acceleration of a body at that time
what is angular motion
movement of a body in a circular path about and axis of rotation
how is angular motion created
eccentric external force applied to a body passing outside of centre of mass
what are the axis’ of rotation
longitudinal
frontal
tranverse
what is the longitudinal axis
runs head to toe through centre of mass
example of skill in longitudinal axis
full spin on ice
what is the transverse axis
runs left to right through centre of mass
example of skill in the transverse axis
cartwheel in gymnastics
what is the frontal axis
runs back to front through centre of mass
example of a skill in the frontal axis
somersault in gymnastics
which plane matches with the longitudinal axis
transverse plane
which plane matches with the transverse axis
frontal plane
which plane matches with the frontal axis
sagittal plane
what are the 3 angular motion descriptors
angular velocity
moment of inertia
angular momentum
what is angular velocity
rate of change in angular displacement / rate of rotation measured in radians per second
how to calculate angular velocity
Angular displacement (rad) / time taken (s)
time takes = rate of rotation
what is one full rotation equal to
2 radians (360)
what is one radian equal to
57.3 degrees
what is moment of inertia
he resistance of a body to change its state of angular motion or rotation / it will resist increasing or decreasing rate of spin (kgm^2)
how to calculate the moment of inertia
sum of (mass x distribution of mass from the axis of rotation)^2
how does mass relate to MOI
greater the distribution of mass = high MOI
slow rate of spin
how does angular velocity and MOI relate
low MOI, high AV - high rate of spin, fast rotation, little resistance
high MOI, low AV - slow rate of spin & high resistance
what is angular momentum
the quantity of angular motion possessed by a body (kgm^2rad/s)
how to calculate angular momentum
moment of inertia x angular velocity
what is the conservation of angular momentum
an analouge of newtons first law
once angular momentum has been generated, it is a product of angular velocity and MOI
- once generated, it is conserved through movement
“a rotating body will continue to turn about its axis of rotation with constant angular momentum unless acted upon by an eccentric force or external torque”
what is angular distance
the distance the body has travelled whilst rotating about an axis
what is angular displacement
shortest route in angular position
what fluid mechanics
study of forces acting on a body in air or water
how does Air resistance and drag affect performance
increase physical demand, leading to early fatigue & poor performances
how does velocity affect AR and drag
increased V = Increased AR & Drag
how does frontal cross sectional area affect AR & Drag
increased FCSA = increased AR & Drag
how does streamlining & shape affect AR & Drag
Increased streamline = lower AR & Drag
how does surface characteristics affect AR & Drag
smooth : lower AR & Drag -> reduce friction
what is projectile motion
movement of a body through the air following a curved flight path under the force of gravity
what is a projectile
a body which is launched into the air losing contact with the ground surface and following a flight path
what is the horizontal distance from the release of a projectile affected by
- speed of release
- angle of release
- height of release
- aerodynamic factors
how does the speed of release affect the horizontal distance travelled by a projectile
- greater force applied = greater the change in momentum therefore greater acceleration
- the greater the outgoing speed, the further it will travel
how does angle of release affect the horizontal distance travelled by a projectile
90 : projectile will accelerate vertically & fall back down (0m)
45 : optimal angle to maximise horizontal distance
< 45 : projectile doesn’t achieve suffient height
> 45 : projectile reaches peak height too quickly & rapidly returns to ground
how does height of release affect the horizontal distance travelled by a projectile
if height of projectile if higher/lower than landing height, optimal angle changes
what affects a projectiles flight path
- relative size of forces acting upon it
- projectile unaffected by AR will have a parabola flight path
how does weight affect flight path
weight dominant - parabolic
air resistance dominant - non parabolic
if a projectile is weigh dominant, what flight path does it follow
parabolic
if a projectile is air resistance dominant, what flight path does it follow
non parabolic
what is Bernoulli lift principle
creation of an additional lift force on a projectile in flight resulting from bernoullis conclusion that the higher the velocity of air flow, the lower the surrounding pressure
how does the shape of a surface effect distance and velocity of the body
curved upper - causes air to travel further & move at higher velocity
flat underneath - causes air to flow a shorter distance & move at lower velocity
how does velocity and pressure affect each other
high velocity , low pressure
low velocity, high pressure
what is the pressure on curved surfaces vs flat
curved - low (due to high velocity)
flat - high (due to low velocity)
how does pressure difference create lift on bodys
fluids move from area of high pressure to low pressure over a body in an aerofoil shape, creating lift
what is an aerofoil
a streamlined body that is capable of generating significantly more lift than drag
how does downwards lift force work
when aerofoil has been inverted ie F1 cars
- increases amount of gravity acting on body to keep it on the ground/prevent lift
how is spin created
applying an external force outside of bodys COM
in what ways can a force change the type of spins generate
topspin
backspin
sidespin hook
sidespin slice
how is topspin created
when force is applied above the COM
what is topspin
spins downwards in transverse axis
- shortens flight path
what is backspin
spins upwards
- lifts
- slows downs
- lengthens flight path
how is backspin created
force applied below the COM
what is sidespin hook
spins left around the longitudinal axis
what creates sidespin hook
force applied to the right of the COM
what is sidespin slice
spins right in the longitudinal axis
how is a sidespin slice created
force applied to the left of COM
what is the magnus effect
creation of an additional magnus force on a spinning projectile which deviates from the flight path
what is a magnus force
a force created from a pressure gradient on opposing surfaces of a spinning body moving through the air
what flight path do spinning bodies follow
non parabolic
what magnus force is created with a topspin
downwards magnus force, shortening flight path
what magnus force is created with backspin
upwards magnus force, lengthening flight path
what magnus force is created is sidespin slice
magnus force to the right , swerving projectile to the right
what magnus force is created is sidespin hook
magnus force to the left, swerving projectile to the left
how does the magnus force link to pressure and velocity of the projectile
occurs when there is high velocity & low pressure
