Biomechanics (1.3) Flashcards
Newton 1st law
law of inertia
“body continues in a state of rest or uniform velocity unless acted upon by an external force”
Newton 2nd law
law of motion
“when a force acts on an object, the rate of change of momentum experienced by that object is proportional to the size of the force and takes place in the direction which the force acts”
Newton 3rd law
“for every action there is an equal and opposite reaction”
velocity def
rate of change of displacement
displacement def
shortest straight line route between two points
momentum def
quantity of motion possessed by a moving body
acceleration def
rate of change in velocity
force def
a push/pull that alters the state of motion of an object
5 effects of force
creates motion accelerate a body decelerate a body change direction of a body change shape of a body
netforce
if net force positive, it will accelerate
if net force negative, it will decelerate
when do balanced forces occur
when net force = 0
friction def
force that opposes the motion of 2 surfaces in contact
what effects air resistance (3)
velocity it is travelling (faster = more ar)
cross sectional area (larger = more ar)
shape (pointy = less)
2 functions of levers
generate muscular effort
increase speed of movement
effort arm
distance from fulcrum to effort
load arm
distance from fulcrum to load
1st class lever + example
fulcrum in middle
heading in football
2nd class lever + example
load in middle
effort arm longer
take off e.g vault
3rd class lever + example
effort in middle
load arm longer
bicep curl
projectile motion def
movement of a body through air, following curved flight path under force of gravity
projectile release def
horizontal distance travelled by a projectile.
Affected by 4 factors
projectile release 4 factors
speed of release
angle of release
height of release
aerodynamic factors of projectile
speed of release
greater force = greater acceleration
angle of release
optimal = usually 45 degrees
height of release
higher up = further distance
flight paths
parabola
non parabola
non parabola flight paths
if air resistance is dominant and weight is small e.g shuttle cock
parabola flight paths
low air resistance, high weight
angular motion def
movement of a body in a circular path, around an axis of rotation
torque def
name for a rotational force
eccentric force def
force that takes place outside centre of mass
3 axis of rotation
longitudinal
transverse
frontal
longitudinal axis
head to toe
through COM
e.g full turn in trampolining
transverse axis
left to right
through COM
e.g front somersault
frontal axis
back to front
through COM
e.g cartwheel
kinematics
study of motion in relation to time and space.
3D image created allowing joint and limb efficiency to be evaluated
4 limb kinematics measurements
bone goniometer
displacement
velocity
acceleration
force plates
.measure reaction force through ground - jumping/running
.can mount on a wall
wind tunnels
analyse:
air resistance/drag
aerodynamic efficiency
e.g DRS/cycle helmets or handles
Bernoulli principle
.higher velocity of air flow = lower surrounding pressure
.if low pressure is above, then high pressure underneath and vice versa
how to create downforce
make surface above flat
how to create upforce
make surface below flat
magnus force def
force created from a pressure gradient on opposing surfaces of a spinning body
magnus effect def
creation of an additional Magnus Force on a spinning projectile, which deviates from the flight path
spide spin hook
side spin which deviates a projectiles flight path to the left
side spin slice
side spin that deviates a projectiles flight path to the right
topspin
eccentric force applied above COM
spins downwards, through transverse axis
backspin
eccentric force applied below COM
spins upwards, through transverse axis
radian
unit of measurement of the angle through which a body rotates
radians equivalents
360 degrees = 2 pie radians
1 radian = 57.3 degrees
angular momentum
.the quantity of angular motion possessed by a body
.must be generated through the use of an eccentric force
.formula!
moment of inertia
resistance of a body to change state of angular motion of rotation
conservation of angular momentum
`as moment of inertia increases, angular velocity decreases, and vice versa
this means
once generated angular momentum is constant, so is a conserved quantity
internal forces
created by muscular contractions acting on the skeleton
external forces (4)
come from outside the body weight reaction force friction air resistance
3 factors effecting friction
roughness of surfaces in contact
temperature of surfaces in contact
size of normal reaction
stability def
ability for a body to resist motion and remain at rest
4 factors affecting stability
mass of object
height of COM
base of support
line of gravity
linear motion def
movement of a body in a straight/curved line, where all parts move the same distance, in the same direction, at the same time
distance def
total length travelled
angular velocity
rate of change of angular displacement
or
rate of rotation
