biomechanical principals (3 laws, centre of mass, factors affecting stability, d+e of scalars speed + dist) Flashcards
3 laws, centre of mass, factors affecting stability, d+e of scalars speed + dist
an increase in friction increases
stability/balance
what has greater inertia, a shot or a tennisball
a shot
what is newtons first law of physics about
inertia
what is inertia
the resistance of a body to move or change its state of motion
linking to inertia, if an object is at rest what will happen
it will remain at rest
linking to inertia if an object is moving in one direction what will happen
it will continue to do so at the same velocity until other forces are exerted upon it
what is the deeper definition of inertia? every ……
every body continues in its state of rest or motion in a straight line, unless compelled to change that state by external forces exerted upon it
simply: a force is required to change the state of motion of that object
the state of motion can be what and changing it means what
still or moving
speeding up or slowing down
what is inertia measured in
kg
the bigger the mass of an object the …….. the inertia, meaning ….
the larger the inertia meaning it is harder to change its motion
what surface can have zero friction
ice
the force acting on an object (in order to overcome inertia) must be ….
unbalanced and larger than inertia
an ice hockey puck will be in a state of ……. before hit and will remain in a …. …….. before it hits the net/wall
state of inertia
in a constant inertia
analyse using newtons 1st law how a footballer will move towards the ball from a stationary position
(2)
they will be in a state of inertia before movement occurs
a force is needed to change their state of motion and over come inertia otherwise they will remain stationary
this force must be unbalanced and larger than inertia
the footballer will provide internal force by contracting their leg muscles (1)
using this force they can overcome inertia allowing them to move from a stationary position and kick the ball from the preferred pitch position (1)
what is newtons second law of physics about
acceleration
what is the equation for 2nd law
force= mass x acceleration
what is the definition for 2nd law
the rate of momentum of a body is proportional to the force causing it AND the change takes place in the direction in which the force acts
2nd law def in simple terms:
more force =
direction force=
more force on object= more acceleration/faster body will go
direction you put the force in = direction body goes
according to 2nd law what remains constant
the mass of the performer
linking to 2nd law the more mass or inertia a body has the more ……. to
the more force it takes to accel the object
analyse using 2nd law how a footballer will move towards the ball from a stationary position
(2)
by varying force of muscle contractions/the number of motor units recruited the footballer can cause a change in momentum for stationary to moving
therefore the greater the force they generate the greater the acceleration to the ball
a swimmer dives of the starting blocks as quick as possible explain how using 1st and 2nd laws
force is applied by the muscles
1st: law of inertia, will remain on the blocks until a force is applied, continues to move forward with constant velocity until another force is applied, water slows the swimmer
2nd: mass of swimmer is constant, greater the force exerted on the blocks the greater the accel/mom, force governs direction
what is newtons 3rd law def
To every action (force) there is an equal and opposite reaction (force)
what is ground reaction force
the equal and opposite force exerted on a performer who applies a muscular force on the ground
what affect does more action force have on the reaction force
the more force applied in the action force the larger the reaction force
net force is the result of ,….
multiple forces
3rd: as a sprinter pushes down and backwards on the ground, the ground…
pushes up and forwards on the sprinter
apply 3rd to a swimmer
swimmer pushes backwards on the water, reaction force thrusts the swimmer forwards
what is the centre of mass
the point at which the mass goes around, the point of balance of a body
if the centre of mass comes out of the base of support what happens
you become unstable
if a person is smaller how does this affect their centre of mass
is it lower
can the centre of mass be outside the body
yes
define and explain the concept of centre of mass in relation to forces (3)
com is a unique point of an object where its weight can be considered to act (1)
object of uniform shape and desity -com/centre of shape
force applied through com/concentric force means the body moves in a straight line/linear motion
force not applied through com/eccentric force means body rotates/angular motion produced
what is a concentric force
a force that is applied through the COM of an object will give it linear motion (will move in a straight line or curve)
what is an eccentric force
a force not applied through the COM is likely to give the object rotation or angular velocity
a smaller person has less …. and therefore we can push their …. outside their ……
less inertia
push com
out bos
what are the key tips about stability
height of centre of gravity
area of bos
line of gravity
mass of performer/object
if your line of gravity is within … then you are stable but
bos
but if it near the edge you are less stable
what is the line of gravity
goes straight down from cog/com
what is stability
maintain balance/equilibrium, resistance to change position
forces altering com can influence/reduce stability
in most cases…….. keep the performer stable by locking …… in place
isometric contractions
locking joints in place
how to males and females com tend to differ
males tend to have higher com due to increased weight in the shoulders
females lower weight around hips
how to improve stability
lower the centre of mass
more contact points/larger area of base of support
define and explain the concept of centre of mass in relation to forces (3)
com is a unique point of object where its weight can be considered to act
object of uniform shape and density- com and centre of shape
force applied through com is concentric and results in body moving in a straight line/linear motion
force not applied through com is eccentric and results in rotation/angular motion
unit for speed
m/s
unit for distance`
m
is speed a scalar or vector
scalar
is distance a scalar or vector
scalar
what is a scalar
when measurements are only described as magnitude/size
what is a vector
forces that have both magnitude/size and direction
definition of distance
length of the path a body follows when moving from one position to another
unit of measurement for distance
m
unit of measurement for speed
m/s
definition of speed
the rate of change of distance
is distance a vector or scalar
scalar
is speed a vector or scalar
scalar
formula for speed
distance covered over
time taken
using newtons laws of motion, explain how a player moves towards a ball during a rally (8)
first law
1st- law of inertia
force is applied by muscles
maintain stationary until force is applied to overcome state of inertia
performer continues to move towards the ball with constant velocity until another force is applied
muscles act as a brake which slows the performer
using newtons laws of motion, explain how a player moves towards a ball during a rally (8)
2nd law
2nd law- law of acceleration
force=mass x accel
mass of performer is constant
greater the force exerted on the ground, greater the accel/mom towards the ball
ground force reaction
force governs direction
using newtons laws of motion, explain how a player moves towards a ball during a rally (8)
3rd law
3rd- law of action and reaction
equal and opposite reaction force
force applied to ground moves performer
using newtons first and second laws explain how the swimmer dives off the starting blocks (4)
1st law
1st law is of inertia
force applied by muscles
performer will remain on the blocks unless a force is applied
performer continues to move forwards with constant velocity until another force is applied
water slows the swimmer
using newtons laws of motion, explain how a player moves towards a ball during a rally (8)
2nd law
2nd law- law of acceleration
force is applied by muscles
mass of swimmer is constant
greater the force applied on the blocks the greater the accel/mom
force governs direction
the final stage of an endurance race usually involves a sprint finish
using 2nd law, explain how an athlete is able to accelerate towards the finish line (3)
force=mass x accel
mass of performer remains constant
force provided by muscular contraction
greater the force exerted on the floor the greater the accel/mom
force governs direction
ground reaction force
tennis player in ready position, use the picture to explain how the msks and nms assist the player in maintaining stability (8)
ao1
biomechanical factors affecting stability: height of com ie lower=more stable, area of base of support ie wider=more stable
msks: muscle attachment to bones and formation of joints allows movements INTO stable positions
nms: two types of muscle contraction, a stationary, stable position would require ISOMETRIC muscle contraction brought about by the RECRUITMENT of muscle fibres
tennis player in ready position, use the picture to explain how the msks and nms assist the player in maintaining stability (8)
AO2
tennis player is bending over=reducing height of com, mass is positioned over bos
flexed the legs at knees and hip, adducted the leg at the hip and dorsiflexed the ankles
by contracting the muscles to move the joints, they can achieve position shown, they require sufficient force/muscle fibre RECRUITMENT to hold the body in that position, contract isometrically
tennis player in ready position, use the picture to explain how the msks and nms assist the player in maintaining stability (8)
AO3
bos is area beneath a person that includes every contact point with supporting surface, greater area=more stable, area between feet so wide feet=more stable when receiving a serve
isometric contracting quads and hams to flex hip and knee=achieve lower com=inc stability, adduction of hip and plantar flexion at the ankles=inc width of a of bos=inc stability
whilst stationary using large motor units to produce force required to maintain position, AONL=all will contract and amount of F produced will be varied by SS, stationary position requires less motor units compared to when they are moving across the court to play the shot
explain how a performer can best maintain stability (8)
AO1
stability is the ability to maintain balance/equilibrium
height of com
area of bos
line of cog
if performer is moving, mass affects stability
explain how a performer can best maintain stability (8)
A02
height of com ie lower=more stable
a of bos ie wider=more stable
line of cog ie closer to bos=more stable
moving/mass ie greater mass=more stable
explain how a performer can best maintain stability (8)
AO3
bos is …… , greater=more stable, by widening feet, or put more hands on the floor like in gym headstand, three point stance in rugby
squatting down will lower com closer to bos=more stable eg martial arts
make sure log stays within bos=more stable
