biomechanics yr 2 Flashcards
linear motion
movement of a body in a straight or curved line, where all parts move the same distance in the same direction over the same time
direct force
a force applied through the COM resulting in linear motion
5 linear motion descriptors
- distance
-displacement
-speed
-velocity
-acceleration / declaration
speed
the rate of change in distance
Angular motion
movement of a body or part of a body in a circular path about man axis of rotation
how does angular motion occur
from an eccentric force being applied to the body known as torque
longitudinal axis
runs from head to toe through the COM
e.g a flat spin of ice or full turn in trampolining
Transverse axis
runs from left to right through the COM.
e.g somersault
frontal axis
from front to back through the COM
e.g cartwheel
3 descriptors of angular motion
- angular velocity
-moment of inertia
-angular momentum
angular velocity
is the rate of change in angular displacement or simply the rate of rotation
angular displacement / time taken
measure in radians per second (rad/s)
moment of inertia
the resistance of a body to change its state of angular motion or rotation
sum of (mass x distribution of there mass from the axis of rotation2)
measured in kgm2
mass effect on moment of inertia
the greater the mass of the body the greater the moment of inertia
Hence, sports with high level of twists etc are performed by athletes with low mass as they can rotate easier and stop rotating with ease.
distribution of mass from the axis of rotation
the further the mass moves away from the axis of rotation the greater the moment of inertia and resistance to change state of motion
Hence, it is more beneficial to tuck around the axis of rotation as your moment of inertia will be lowered therefore you can rotate more quickly.
distribution of mass when running
recovery leg- mass is distributed close to the axis of rotation at the hip therefore moment of inertia is low and the leg moves back down quickly
drive leg- mass distributed further away from the axis of rotation therefore moment of inertia is higher and leg moves slowly
moment of inertia’s effect on angular velocity
if moment of inertia is high, resistance to rotation is high therefore angular velocity is low and the rate of the spin is slow
if moment of inertia is low resistance to rotation is low therefore angular velocity is high and spin rate is high
angular momentum
the quantity of angular motion possessed on a body
moment of inertia x angular velocity
angular analogue of newtons first law
’ a rotating body will continue to turn about an axis of rotation with constant angular momentum unless acted upon by an eccentric force or external torque’
fluid mechanics
the study of the forces acting on a body travelling through air or water
4 factors that affect levels of drag and AR
Velocity - the greater the velocity the greater drag and AR
Frontal CSA - larger the frontal CSA the larger the AR or drag.
Streamlining or shape - more streamlined for aerodynamic the shape of the body in motion the lower the Ar and drag
surface characteristics - the smoother the surface the reduced amount of Ar and drag there is
how do skiers minimise AR
smoothness of their lycra
minimise the FCSA by adopting a low couched position
wear tear dropped helmets to create streamlined shape
projectile motion
movement of a body through the air following a curved flight path under the force of gravity
projectile
a body that is launched into the air losing contact with the ground surface
4 factors that affect horizontal distance
speed of release
height of release
angle of release
aerodynamic factors