PAPER 1 - Biomechanics Flashcards
Define Newton’s First law of motion : INERTIA
a body continues in a STATE OF REST or UNIFORM VELOCITY unless acted upon by an EXTERNAL or UNBALANCED FORCE
Define Newton’s Second law of motion : ACCELERATION
a body’s RATE OF CHANGE in MOMENTUM is PROPORTIONAL to the SIZE of the FORCE applied and acts in the SAME DIRECTION as the force applied
Define Newton’s Third law of motion : REACTION
for every ACTION FORCE applied to a body there is an EQUAL and OPPOSITE reaction force
What is the equation for VELOCITY ?
velocity = displacement / time taken
What is the equation for MOMENTUM ?
momentum = mass x velocity
What is the equation for ACCELERATION ?
acceleration = (final velocity - initial velocity) / time taken
What is the equation for FORCE ?
force = mass x acceleration
Define FORCE
a PUSH or PULL that ALTERS that state of motion of a body
Define INTERTIA
the RESISTANCE of a body to CHANGE its state of motion, whether at rest or while moving
Define VELOCITY
the RATE OF CHANGE in DISPLACEMENT
Define MOMENTUM
the QUANTITY of MOTION possessed by a body
Define ACCELERATION
the RATE OF CHANGE in VELOCITY
Define WEIGHT
GRAVITATIONAL PULL that the earth exerts on the body - (N)
Define REACTION
EQUAL AND OPPOSITE FORCE in response to the action force placed upon it
Define FRICTION
the force that OPPOSES the motion of TWO SURFACES in contact
Define AIR RESISTANCE
a force that OPPOSES the MOTION of a body TRAVELLING through the air
What are LIMB KINETICS ?
- study movement in relation to TIME AND SPACE
- white dots
What are FORCE PLATES ?
- measure ground reaction forces
What are WIND TUNNELS ?
- test aerodynamic efficiency
- measure air resistance
Define CENTRE OF MASS
the point at which a body is BALANCED in ALL DIRECTIONS
How do you increase stability ?
- increase mass = increase inertia
- decrease CoM
- increase BoS
- more central LoG
Define LINE OF GRAVITY
imaginary line that extends from the COM downwards to the FLOOR
What is a FIRST CLASS lever ?
effort - fulcrum - load
What is a SECOND CLASS lever ?
effort - load - fulcrum
What is a THIRD CLASS lever ?
load - effort - fulcrum
What is the EFFORT ARM ?
distance from the FULCRUM to the EFFORT
What is the LOAD ARM ?
distance from the LOAD to the FULCRUM
What is MECHANICAL ADVANTAGE ?
SECOND CLASS
- effort arm is greater than the load arm
- large load / small effort
- slower
What is MECHANICAL DISADVANTAGE ?
THIRD CLASS
- load arm is greater than effort arm
- small load / large effort
- faster
What is an INTERNAL FORCE ?
generated by the CONTRACTION of SKELETAL MUSCLE
INTERNAL FORCE : EXAMPLE
100m - contract rectus femoris - extend knee - drive away from the blocks
What is an EXTERNAL FORCE ?
comes from OUTSIDE the body and acts upon it
What are the 4 examples of EXTERNAL FORCES ?
- weight
- reaction
- friction
- air resistance
What are the 5 effects of FORCE ?
- create motion
- accelerate a body
- decelerate a body
- changing the direction
- changing the shape
Using a football penalty as an example: how does force (1) CREATE MOTION ?
the football will remain at rest on the penalty spot until a force is applied to it
Using a football penalty as an example: how does force (2) ACCELERATE A BODY ?
the greater the force applied by the footballer’s foot to the ball, the greater the rate of acceleration towards the goal
Using a football penalty as an example: how does force (3) DECELERATE A BODY ?
as the ball moves through the air towards the goal, the force of AIR RESISTANCE will act in the OPPOSITE direction and slow it down
Using a football penalty as an example: how does force (4) CHANGE THE DIRECTION OF A BODY ?
as the goalkeeper dives to save a high corner shot, he will apply force from his HANDS to the BALL, changing it’s direction pushing it AWAY from the goal
Using a football penalty as an example: how does force (5) CHANGE THE SHAPE OF A BODY ?
if the goalkeeper fails to make the save, the force of the ball coming into contact with the NET will change the shape of the net.
What is NET FORCE ? (resultant force)
sum of all the forces action on a body - when all individual forces have been considered
What is the net force when forces are BALANCED ?
net force = 0
What are BALANCED FORCES ?
two or more forces action on a body are EQUAL IN SIZE and OPPOSITE IN DIRECTION
What are UNBALANCED FORCES ?
two or more forces UNEQUAL IN SIZE and OPPOSITE IN DIRECTION = net force
What are the 2 VERTICAL FORCES ?
weight
reaction
What is the equation for WEIGHT ?
mass x acceleration due to gravity
What are the 2 HORIZONTAL FORCES ?
friction
air resistance
What 4 factors affect FRICTION ?
- roughness of ground surface
- roughness of contact surface
- temperature
- size of normal reaction
How does (1) ROUGHNESS OF GROUND SURFACE affect friction ?
increasing roughness = increased friction
How does (2) ROUGHNESS OF CONTACT SURFACE affect friction ?
increasing roughness = increasing friction
How does (3) TEMPERATURE affect friction ?
increasing temperature = increasing friction
e.g. F1 drivers have warm up lap
How does (4) SIZE OF NORMAL REACTION affect friction ?
increasing normal reaction = increasing friction
e.g. shot-putters have high mass - equal / opposite high reaction force - greater friction - prevents over-rotation
What 4 factors is AIR RESISTANCE affected by ?
- velocity
- shape
- frontal cross-sectional area
- smoothness of surface
How does (1) VELOCITY affect air resistance ?
increasing velocity = increasing air resistance
How does (2) SHAPE affect air resistance ?
increased aerodynamic = decreasing air resistance
What is STREAMLINING ?
creation of SMOOTH AIR FLOW around an AERODYNAMIC shape to minimise air resistance
How does (3) FRONTAL CROSS-SECTIONAL AREA affect air resistance ?
decreasing frontal cross-sectional area = decreasing air resistance
How does (4) SMOOTHNESS OF SURFACE affect air resistance ?
increasing smoothness = decreasing air resistance
What are the units for velocity ?
metres per second - m/s
What are the units for acceleration ?
metres per second per second - m/s/s
What are the units for momentum ?
kilogram metres per second - kgm/s
What are the units for force ?
newtons - N
What are the units for weight ?
newtons - N
What is RELIABILITY ?
the extent to which an experiments produces the SAME RESULT after REPEATED TRIALS
What is VALIDITY ?
how well a test measures what it claims to measure = accurate application and interpretation
What is 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
What is DIRECT FORCE ?
a force applied through the CoM resulting in LINEAR MOTION
What is DISTANCE ?
the total length covered from start to finish (m)
What is DISPLACEMENT ?
the shortest straight-line route from start to finish (m)
What is SPEED ?
the rate of change in DISTANCE (m/s)
What is a DISTANCE/TIME graph ?
a visual representation of the DISTANCE travelled plotted AGAINST the TIME taken
What is a SPEED/TIME graph ?
a visual representation of the SPEED OF MOTION plotted AGAINST the TIME taken
What is VELOCITY/TIME graph ?
a visual representation of the VELOCITY OF MOTION plotted against the TIME taken
What is ANGULAR MOTION ?
movement of a body or part of a body in a CIRCULAR PATH about an AXIS OF ROTATION
What is an ECCENTRIC FORCE ?
a force applied OUTSIDE the CoM, resulting in ANGULAR MOTION
What is a TORQUE ?
a MEASURE of the TURNING force applied to a body
What is a sporting example of linear motion ?
skeleton bob at top speed
What is a sporting example of angular motion ?
gymnastic somersault
Where does the LONGITUDINAL AXIS run ?
from head to toe (through the CoM)
Where does the TRANSVERSE AXIS run ?
from left to right (through the CoM)
Where does the FRONTAL AXIS run ?
from front to back (through the CoM)
What sport skill occurs in the longitudinal axis ?
flat spin on ice
What sport skill occurs in the transverse axis ?
somersault
What sport skill occurs in the frontal axis ?
cartwheel
What is ANGULAR VELOCITY ?
the rate of change in ANGULAR DISPLACEMENT (radians per second)
What is MOMENT OF INERTIA ?
the RESISTANCE of a body to change its state of ANGULAR MOTION or ROTATION
How do you calculate moment of inertia ?
mass x distance from axis
What is ANGULAR MOMENTUM ?
the QUANTITY of ANGULAR MOTION possessed by a body
what is angular motion?
the movement of a body in circular motion around an axis of rotation
when does angular motion occur?
when an eccentric force is applied to the body from outside the body
give an example of angular motion?
cartwheel or somersault
what is newtons first law also known as?
law of inertiaw
what is the law of inertia?
a body will remain at rest or constant velocity unless acted upon by an external force
how is angular motion similar to law of inertia?
angular motions continues until acted on by an external force
what are the principal axis in angular motion?
longitudinal, transverse, frontal
what is the longitudinal principal axis?
runs from top to bottom
give a practical example of the principal axis: longitudinal?
pivot in netball/ fast spin in ice skating/pirouette
give a practical example of the principal axis: transverse?
somersault on a beam in gymnastics/forward roll
what is the transverse principal axis?
runs from side to side
what is the frontal axis of rotation?
runs from front to back
give a practical example of the principal axis: frontal?
cartwheel on a beam in gymnastics
what is angular distance?
the length of the angular path travelled from one position to another
what is angular displacement?
the shortest straight line angular route from start to finish
what is angular distance/displacement measured in?
radians
what is angular speed?
the rate of change of angular distance
what is angular speed measure in?
radians/s
equation for angular speed?
angular distance/time
what is angular velocity?
rate of change of angular displacement
equation for angular velocity and units?
angular displacement/time
radians/s
what is the moment of inertia?
the resistance a body has to change its state of angular motion or inertia
equation of moment of inertia?
sum of[mass x distribution of mass from axis of rotation]
what is moment of inertia measured in?
kg/m2
what is fluid dynamics?
the forces acting on an athlete when in the air or water
what force act on an athlete in the air?
air resistance
what force acts on an athlete in the water?
drag
are air resistance and drag good or bad? If bad what needs to be done?
they both act in opposite direction to the body’s motion so need to be minimised to reduce their effects
movement of a body on land affected by…
air resistance
movement of a body through the air…
projectile motion
movement of a body through water affected by…
drag
fluid dynamics adaptations in downhill skiing (3)
- lowered body position which decreases their frontal cross sectional area
- tear drop shaped helmet
- silky suits as a smooth surface/shaved arms and legs
fluid dynamics adaptations in track cycling (4)
- lightweight carbon fibre bike design which reduces air resistance due to its aerodynamic features
- shoulders forward and tilted body and narrow handlebars reduces frontal cross sectional area
- pointed helmets to streamline air flow over the head
- shaved legs and tight suit to act as a smooth surface
what are the 5 factors that affect air resistance/drag?
- mass
- velocity
- frontal cross sectional area
- smooth surface
- streamlining and shape
what affect does increased velocity have on air resistance/drag?
increased velocity, increases AR/drag so velocity cannot be reduced to minimise AR/drag
what causes a low moment of inertia?
having a tight body position (close together)
what does a low moment of inertia do to rotation?
makes rotation easier
what causes a high moment of inertia?
having a stretched out body position
what does a high moment of inertia do to rotation?
makes rotation harder
what are the two factors that affect moment of inertia?
mass and distribution of mass about the axis of rotation
how does mass affect moment of inertia?
higher mass causes a higher moment of inertia so it is harder to rotate - less mass causes lower moment of inertia so it is easier to rotate
give a prac example of low mass affected moment of inertia?
a gymnast would want a lower mass so that they have a lower moment of inertia so that it makes it easier for them to rotate in a routine (and uses less eccentric forces)
give a prac example of a high mass affecting moment of inertia?
a sumo wrestler would want to have a higher mass so they would have a higher moment of inertia so makes it harder for them to rotate and therefore harder for them to be pushed over by their opponent
how does the distribution of mass around an axis of rotation affect moment of inertia?
the further the mass from the axis the higher the moment of inertia - the closer the mass to the axis the lower the moment of inertia
give a prac example of far distribution of mass from axis of rotation affecting moment of inertia?
a diver would have a straight body position so their mass would be distributed far from the axis therefore leads to a higher moment of inertia therefore harder to rotate
give a prac example of close distribution of mass from axis of rotation affecting moment of inertia?
a low spin in ice skating would have more mass closer to the axis of rotation which lowers the moment of inertia and makes rotation easier so they can easily spin on the ice with less eccentric force applied
what is the relationship between moment of inertia and angular velocity?
higher moment of inertia means that it is harder to rotate so the angular velocity decreases
lower moment of inertia makes it easier to rotate so the angular velocity increases
what is the equation for angular momentum?
moment of inertia x angular velocity
units for angular momentum?
kgm2 radians/s
what is moment of inertia units?
kgm2
angular velocity units?
radians/s
what affect does increased mass have on air resistance/drag?
higher mass leads to air resistance/ drag having less of an impact on the bodyg
give a prac example of mass of the body affecting the air resistance/drag?
a golf ball vs table tennis ball
air resistance/ drag affects the table tennis ball more because it has less mass
the golf ball has more mass so it has more velocity
what affect does frontal cross sectional area have on air resistance/drag?
higher frontal cross sectional area means that air resistance/drag increases
lower frontal cross sectional area means that less air makes contact with the body so less air resistance/drag
give a prac example of low frontal cross sectional are affecting AR/drag?
cyclists lower their body position and have thin bikes so there is less area for the air to make contact with so reduces the affect of AR/drag
give a prac example of high frontal cross sectional area affecting AR/drag?
track cyclists or downhill skiing having high frontal cross SA would increase AR/drag so makes them slow down
therefore negative affect
what effect does streamlining and shape have on AR/drag?
the more streamlined a body, the less air resistance as it creates a smoother surface to air to flow around the body
more aerodynamic shape…
…reduced AR/drag
describe a practical example of a swimmer using streamlining to their advantage?
- they wear a cap so this creates a smoother surface
- they shave arms/legs for a smoother surface
- wear less clothes and tighter fitted also creates a smoother surface
- narrow technique so that it is more streamlined over their shoulders
how does a swimmer shaving their body help performance?
creates a smoother surface and provides less obstruction through air/water
when does parabolic flight occur?
if the weight is the dominant force and air resistance is smaller
give a prac example of a sport that would produce a parabola?
shotput (as weight > AR)
in flight projectiles are always affected by what 2 forces?
weight and AR
when does non-parabolic flight occur?
when the AR is the dominant force, and weight is smaller
give prac examples of non parabolic flight?
shuttlecock, javelin, discus
how does height of release and angle of release affect a projectile?
45 degrees is only the optimal angle if release height = landing height
if release height is ABOVE landing height then the angle of release should be < 45 degrees
if the release height is BELOW the landing height then the angle of release should be > 45 degrees
what is the optimal angle of release for a projectile?
45 degrees
give a prac example of when the release height is above the landing height in projectiles?
javelin or tennis serve
give a prac example of when the release height is below the landing height in projectiles?
basketball shot
how does speed of release affect a projectile in flight?
links to newtons 2nd law which says a greater force would cause a greater acceleration
eg: greater force applied to a shotput causes a greater acceleration
when drawing free body diagrams for projectiles, what are the two main forces that act on the body and where should they originate from?
weight and AR
should originate from the COM
what is the aerofoil shape?
curved ontop
flat on the bottom
what does Bernoulli’s principle tell us about air travelling over an aerofoil shape?
air has to travel a longer distance over the top (curved) so this leads to greater air velocity and speed BUT decreases pressure
air travels a shorter distance underneath so has a lower air velocity and a higher pressure
in bernoulli’s principle, high velocity = ? pressure
low pressure
in bernoulli’s principle, a higher pressure underneath compared to ontop leads to what?
higher pressure underneath causes LIFT
this means the body will stay in flight for higher and longer
what angle should a discus be thrown the optimise flight?
17 degrees
as it does not have an aerofoil shape changing the angle causes a greater air velocity ontop therefore this increases the pressure below and generates LIFT
what is a magnus force?
the creation of a force on a spinning projectile that causes it to deviate from the flight path.
how is spin created?
by applying an eccentric force outside the COM
does spin create a parabolic or non parabolic flight?
all types of spin create non parabolic flight
