biomechanics Flashcards
define moment of inertia
is the bodys resistance to change in its state of angular/rotational force
what’s the formula for moment of inertia
MOI= radius of rotation x mass
decreaced inertia means…
increased angular velocity
if a figure skater has their legs and arms out whilst spining does this have more or less inertia
more inertia
flexion creates more or less MOI ?
less
draw a graph that describes the conservation of angular momentum including angular velocity and moment of inertia
straight line = angular momentum
low then high then low- moment of inertia
high then low then high= angular velocity
define angular momentum
is the rotational or angular motion possessed by an object
how do you increase angular momentum
startt off with a jump or run up or improve segmental interaction take off
define the different leavers including: axis/fulcrum, effort/for arm, resistance arm, input(effort) force, output (resistance force)
fulcrum/ axis- point around which the lever rotates
effort/ force arm- the distance between the fulcrum and the point at which the force is applied
resistance arm- the distance between the fulcrum and the centre of resistance
input force (effort)- force exerted ON the lever
output( resistance force) -force exerted BY the lever
draw a diagram of first class lever and provide an example
tricep extention
header
force(down) fulcrum resistance (up)
draw a diagram of a second class lever and provide an example
fulcrum resistance force
push up
draw a diagram of a third class lever and provide an example
fulcrum force and resistance
bicep curl
list the factors effecting levers
- length of levers
- inertia of the lever
- the amount of force
describe factor effecting levers: the length of levers
velocity is greatest at the distal end of the lever
- longer lever greater at impact
- club length increased = increased velocity and momnetum at impact provide the athlete can control the longer lever as italso has an increased mass
- childern and begginers hsould start with a smaller length so its easier
describe the factor effecting levers in terms of inertia of the lever
- the longer the leaver the heaveir it is and therefore the more difficult it is to rotate
- by gripping down the club in striking sports athlete can reduce the rotational inertia and implement therefore making it easier to swing bunting
describe the factor effecting levers in terms of the amount of force
- the amount of force an athlete is able to generate via their muscles determines the length of the lever the athletes should use
- longer levers are usually heavier, therefore more force is required to move them.
describe newtons 1st law
the 1st law states that an object will remain at rest unless acted on by an external force. the object will move in the direction of the force acted upon the object
inertia is a object resistance to change in it current state or position, an objects inertia is proportional to its mass
describe newtons 3rd law
- states for every action there will be an equal and opposite reaction.
- if an athlete directs their foot towards the grounf then there will be a ground reaction force of equal force magnitude directed back in the direction towards the athletes foot
example: sprinter or swimmer using blocks to push the athlete forwards.
- tumble turn
describe newtons 2nd law
that an objects acceleration is direactly proportionsla to the force acting upon it and its indirectly proportional to its mass.
the greater the force applied to the object the greater the acceleration
f=ma
state the formula to increase momentum
f=ma to increase momentum we can increase mass or increase in velocity of the object.
- an object can only have momenttum if its moving
describe force motion
relates to the magnitude of the force and the direction of the force applied.
athlete pushing strinking kicking applying max effort will effectivley maximise the magnitude of the force applied.
direction of the force applied- force in the direction of the target to increase transfer of momentum through the ball/object
what is the force-time relationship
where the acceleration of the object is proportional to the force applied and the impulse is the change in momentum.
how do you create a larger impulse
increase the range of motion in preparation phase of throwing an object
eg. discus throw and windup to increse impulse
explain how an archer can adust their technique with the bowstring to increase the force time relationship
the longer time in contact with the bowstring and the further back the bowting is drawn the greater the impulse applied and the faster and straighter the arrow will go
draw 2 different graphs relating to time force
graph one - short period of time short amount of high force
graph 2 longer period of time lower amount of force.
name an explain the biomechanicle principle behind having foam on the sole of running shoes and identify the benefit to a runner
biomechanical principle is force time (impulse)
- impulse is a measure of force applied over time the equation is impulse= force x time
foam increases the time the force is applied by the foot
absorbs impact and decreases peak force
the benefits to the runner is that it prevents injury
when stopping a force we…
usually increase the time components so we can decrease the peak force
define coefficient of restitution (COR)
refers to the elasticity of an object. the COR determines the measure of momentum that is conserved.
if momentum is perfectly conserved the COR is 1 but if the momentum is imperfect /not conserved the its less than 1 and if its no moving its 0
what are the 3 factors that effect the COR of an object
- the material of the surface
- velocity of collision, if the velocity of an object is increased then the COR is decreased as its altering the shape of the object once hit the ground due to a large amount of force
- temperature of the materials - as temperature increases so does the COR such as squash
in relation to the biomechanical principle of force motion explain how the raised lip at the rear end of a swimming block improves perforcance.
allows force to be applied by the swimmer in more of the horizontal direction
thus causing a decrease in the swimmers times because the new blocks allow swimmer to increase their starting accleration.
by producing more force in the direction the swimmer needs to go
would a beginner tennis player use a ball with a higher COR? why/why not?
no, they need a lower COR as the ball has less elasticity meaning that the ball will be less bouncy and can be better controlled and as beginners are needed to have more control on the ball and hit the ball at a slower velocity
define torque
a force that produced a rotational movement around an axis point (angular motion) from from an eccentric force (rotational “off centre” force)
torque= perpendicular distance x force
how is torque increased
the increasing application of force generated by the muscular contraction of the athlete
something with a greater radius means less force is required to still get maximal accelleration
and angle
define segmental interaction
- is the transfer of energy/ momentum between body parts. it is the way the body interacts to meet demands of the task.
what are the 6 characteristics of segmental interaction
- body parts move in a sequence to produce large amount of force
- starts with largest, strongest and slowest then smallest and fastest resulting in a summation of force
- the next segment begins to move as the proceeding has reached max velocity
- need to be well balanced to aid transfer
- follow through to prevent deaccelleration of last segment & safe dissapation of force
- all forces are directed towards the target
provide an example of segmental interaction
baseball pitcher
legs, trunk, arm, shoulder, elbow and wrist the AM transferrred from lrg to sml groups
…. continue to list all 6 characteristics
describe co-ordination continuum
the sequencing approach to develop motion.
by co-ordinating segments transferring AV at its peak to produce max force.
define balance and 4 ways to improve balance
the ability to maintain its position
- widens base of support = standin shoulder width apart
- increase SA to ground( points of contact) by standing flat footed
- lower COG by bending knees
- maintian line of gravity in the middle of base of support e.g. butt out head in middle
descibe the range of motion
the degreee at which a body segment moves around a joint while in motion
- by extending arm in preparation phase allows a higher force production
what 3 things can cause optimal projection
- height of release
- projection angle
- velocity of release
describe turbulant flow
flow in which the velocity at which any point varies erradically.
- seperates late
- less pressure
describe laminar flow
a type of fluid flow in which fluid moves smoothly in individual layers or streams
- seperates early
- more pressure
what is form (pressure) drag
is the resistance created by the pressure differential between the front and the back of an object moving a fluid (air/water)
- reducing cross sectional area decreases form drag when being in aerodynamic position
why is a cyclist helmet tapered towards the back
to delay the seperation of the air particles traveling over the helmet
what is the boundary separation layer
the point at which the boundary layer of fluid passing over the body/onject separaes from the surfaceis known as the boundary layer separation point.
- for examples golf balls have dimples because they delay the boundary layer separation point
define surface drag (skin friction) and how it can be decreased
is the friction between the fluid (air/water) and the surface of a moving object
smooth, tightly fitting material will decrease drag such as swimming caps
define wave drag and how it can be reduced
- the resitance formed by the creation of waves at the point where air and water interact
- this drag comes from the creation of waves as an object (swimmer/boat) moves through water.
improving buoyancing (eg wearing wetsuit)
making the body /obect more streamlined and improving technique of the swimmer
what are the different types of drag
form drag
surface drag
wave drag
define bernoullis principle
the velocity of the fluid flow determines tge pressure systme
- pressure on one side of an object is inversly proportional to the velocity on the same side of the object.
- As the velocity of the fluid increases the pressure decreases.
explain how bernoullis principle assists in keeping the frisbee in the air longer and thus enhancing the distance it travels. drw and labell a diagram to assist your explaination (5mark)
draw diagram with low pressure on top high on bottom adds direction drag, lift and eccentric force
benuellis principle states the velocity of the fluid flow determines the pressure system. high pressure systme move to low pressure systems causing a lift force on the frisbee
- the shape of the frisbee allows LV HP to be created underneath and HV LP above the frisbee
list some things that effect torque
- angle
- moment arm
- force
define the magnus effect
the pressure differential, high on one side and low on the other, creates a lift force (the magnus force) that causes the ball to move in the direction of the pressure differntial (from high to low)
- magnus force changes the flight path of the ball due to spin while moving through the air.
describe why a second class lever system has a high mechanical advantage
the force arm is longer then the resistance arm which allows a heavy load to be lifted more efficiently/ less force required to move the load
At the commencement of the downswing, the player flexes his elbows and brings the club closer to his axis of rotation. Why does he do this and which biomechanical principle does it relate to?
Moment of inertia/angular inertia (1 mark)
When the mass is closer to the axis of rotation, its easier to manipulate (1 mark) and therefore he does this to increase the angular velocity at the commencement of the swing (1 mark)
The spin technique is very difficult to master as it involves many biomechanical principles. Identify two biomechanical principles used in the spin that would impact the throwing of the discus.
Impulse (force-time) (1 mark)
By completing the spin, the athlete has a longer time to produce a force on the disc (1 mark)
With more time producing a force, more force will be transferred to the disc after the spin. Greater end force equals longer distance (1 mark)
Force motion (1 mark)
By spinning, the athlete generates a greater velocity through the increased acceleration of body parts (1 mark)
This increased acceleration will produce a greater force according to Newton’s 2nd law. Greater end force equals longer distance (1 mark)
in relation to a tackle what newtons law affects it the most
newtons 2nd law
the greater the bodys momentum the more force that needs to be applied to either stop or slow the player down.
- as a result when two bodies collide, the one with the most momentum will be less affected.
how can a tackler increase impulse
by increasing force applied by:
- increasing velocity of the incoming tackler
- increase strengths/mass by going to the gym
- incorporate segmental interaction to produce greater force
give an application of moment of inertia in regards to swimming
higher elbow brings the mass closer to the axis of rotation/reducing radius of rotation thus decreasing moment of inertia.
- chealsea can swim with less effort (more efficiently) required to rotate her arm or recovering her arm at a higher velocity
in relation to force time how doeas sarah throw a ball faster
by producing a greater impulse
- having greater ROM
- principles of segmental interaction
- later release point
- greater follow through
how does a soccer player create topspin
by applyinf an eccentric force above the centre of the ball.
on the topside of the ball the boundary lyer of air will be colliding with the oncoming air creating a highpressure (low velocity) area of the ball
on the bottom side of the ball the boundary layer will be moving in the same direction as the air passinf by so ther is no collision creating low pressure (high velocity)
pressure differential causes the ball to move from an area of high p to low p cthus creates a lift force called the magnus effect
characteristics of topspin and back spin
topspin- causes ball to dip/drop quickly traveling less distance. bounce off at a lower angle
back spinon a ball causes it to ris ehigher in the air and travel further.
if a golfer swings with the sam eforce and technique in relation to the clubs of 10, 20, 30 and 40 degree clubs which angle will have the greatests distance
10 greatest distance ad 40 less didtance due to trajectory.
why does a dimpled golf ball travel further than a smooth golf ball
a dimpled golf ball has a smaller area of turbulant air behind it, thus decreasing drag. there is also a later boundary separation
what are the different levers for a person standing on their tip toes and elbow flexion to do a bicep curl
plantar flexion = second class
bicep= third class
a drop shot played in tennis would be best executed by placing which typ eof spin on the ball?
back spin
is it true that velocity before is greater than after the bounce
yes
the event was to change from freestyle skiing (tricks/jumps) to long-distance ski jumping, an event where competitors take off from a ramp 120m above landing height, describe how the athlete’s angle of release would change at the point of take-off? Furthermore, what type of drag would have the most significant impact on the distance achieved by the jumper?
Demands of the task have changed from large vertical displacement to large horizontal displacement (1 mark)
Therefore the athlete would take off at a reduced angle to maximise the horizontal component achieved (1 mark)
Profile/form drag (1 mark)
Use your understanding of drag and lift to discuss how the angle of attack of a discus (5o, 45o, 85o) affects the distance achieved.
If the angle of the discus is too flat (5) to the oncoming resistance, then drag will be minimised (1 mark) however, there will be no lift created, and subsequently, the total distance will be low (1 mark)
If the angle of the discus is too great (85), then lift will be high (1 mark); however, drag will also be high due to the increased cross-sectional area presented to the oncoming air, reducing overall distance (1 mark)
If the angle of the discus is optimal (45), then the right balance between lift being maximised (1 mark) whilst drag is minimised is attained, allowing for maximal distance to be achieved.(1 mark)
Compare and contrast the projectile motion requirements for the two skills pictured below.
basketball free throw and soccer kick
Velocity of release - soccer maximises the velocity of release (1 mark) vs Basketball free throw - reduced velocity of release due to less distance requirement (1 mark)
The angle of release - soccer 45o, assuming all other factors are held equal to allow for maximum distance (1 mark) vs basketball free-throw - increase the angle of release to increase accuracy and likelihood of ball going in (1 mark)
Height of release - not relevant in soccer goal kick(1 mark) vs basketball want to increase the height of release for improved accuracy (1 mark)
explain the biomechanics behind how the curveball moves away from a right handed hitter
DESCRIBE SPIN
applied an off center or eccentric force
- magnus force changed flight path of the ball due to spin while moving through the air.
-airflow around the spinning ball (boundary layer) goin in the same direction as onsoming air creates high velocity
- areas of HV form a low pressure system
- airflow around the spinning ball (boundary layer) going in the opposite direction as oncoming air create low velocity
- areas on LV from a high pressure system
air moving from high to low pressure causes the ball to moe in the same direction
identifies that the movement of air creates a lift/magnus force.
explain the type of spin and why a golf balls flight path curves
- back spin
hit off centre/eccentric force
low-pressure area occurs where airflow of spin (boundary layer) goes
in the same direction as oncoming air/high velocity
high-pressure area occurs where airflow of spin (boundary layer) goes
against direction of oncoming air/low velocity
air/object moves from area of high pressure to area of low pressure
or lift/magnus force is created from air moving from area of high
pressure to area of low pressure.
