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pes yr 12 > biomechanics > Flashcards

biomechanics Flashcards

1
Q

define moment of inertia

A

a body’s resistance to a change in its state of angular/rotational force

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2
Q

when angular velocity is high…

A

MOI is low

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3
Q

when MOI is high,,,

A

angular velocity is low

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4
Q

what always stays constant

A

angular momentum

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5
Q

why does a figure skater spin faster when tucked in?

A

high angular velocity, reduced MOI.

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6
Q

what law does angular momentum apply to? define the law?

A

Newtons 1st law - an object remains in constant motion unless external forces act upon it.

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7
Q

where is the fulcrum in a first class lever

A

between the force and resistance

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8
Q

where is the fulcrum in a second class lever

A

closest to the resistance

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9
Q

where is the fulcrum in a third class lever

A

closer to the force

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10
Q

what does a large resistance arm ensure? and why is this type of lever the most common in the human body?

A

an increase in speed can be obtained.
because we are built for speed.

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11
Q

if the fulcrum is closer to the resistance…

A

it is easier to lift the load.

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12
Q

what is the second class lever mechanical advantage

A

the force arm is longer than the resistance arm, meaning it is able to lift heavier loads more efficiently.

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13
Q

what is the third class mechanical advantage

A

the longer resistance arm allows for greater force transfer as it is able to generate a greater velocity.

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14
Q

what 3 factors affect levers

A

length of the lever
inertia of the lever
amount of force

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15
Q

why does inertia effect a lever

A

the longer a lever, the heavier it is usually. this means its more difficult to rotate

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16
Q

what is newtons 1st law

A

an object will remain at rest unless acted upon by an external force.

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17
Q

what is newtons 2nd law

A

an objects acceleration is directly proportional to the force acting upon it and is indirectly proportional to its mass
F = ma

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18
Q

newtons 2nd law explains that: the greater the force applied to the object…

A

the greater acceleration.

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19
Q

what is newtons 3rd law

A

for every action there is an equal and opposite reaction.

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20
Q

define force motion

A

relates to the magnitude of force and the direction of the force applied.

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21
Q

how can we increase momentum

A

by increasing the mass or the velocity of an object.

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22
Q

what will happen if an athlete extends the duration they’re in contact with an object? what principle does this relate to?

A

increased impulse
force time

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23
Q

define impulse and give the equation

A

the change in momentum
impulse = force x time

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24
Q

how can a larger impulse be created

A

increasing ROM - extended duration

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25
Q

the greater the impulse…

A

the greater velocity transferred into the object and the further distance the object will travel

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26
Q

how can force absorption reduce impact related injuries

A

because we are reducing the impulse by absorbing force over a long period of time.

27
Q

define coefficient of Restitution

A

determines the ratio of relative velocity after impact to the relative velocity before collision

28
Q

what does the COR determine

A

the measure of momentum conserved - perfectly conserved (1.0), imperfectly conserved (0)

29
Q

what 3 factors affect the COR

A

materials of interacting surface
velocity of collision
temperature of materials

30
Q

define torque

A

a force that produces a rotational movement around an axis point from an off-centre eccentric force

31
Q

what is the equation for torque

A

torque = force x perpendicular distance of the moment arm.

32
Q

why does a greater radius require less force?

A

because the perpendicular distance of the moment arm is increased, meaning that not as much force is required to produce movement

33
Q

define segmental interaction

A

the transfer of energy and momentum between body parts. it is the way the body segments and interacts to meet the demands of the task.

34
Q

what are the 6 points to segmental interaction.

A
  1. body parts move in a sequence to generate the largest force or acceleration possible.
  2. movement starts with the largest, slowest, and strongest segments, moving through to the smallest and fastest, resulting in summation of momentum
  3. the next segment begins to move as the preceding segment has reached maximum velocity, allowing for effective timing.
  4. the body needs to be well balanced to aid the transfer of momentum across body parts.
  5. follow through is Important to prevent deceleration of the last segment and safe dissipation of force
  6. all forces are directed towards the target.
35
Q

what is the coordination continuum

A

the sequencing approach to develop motion through correct timing of body parts.

36
Q

define balance

A

the ability of something to maintain and hold its position.

37
Q

how can we achieve greater balance

A

widen base of support
increase contact points to the ground
lower centre of gravity
maintain line of gravity.

38
Q

define ROM

A

the degree at which a body segment moves around a joint while in motion.

39
Q

what are the 3 parts of optimal projection and define them

A

height of release - the position above the ground of which the athlete releases the ball
angle of release - the angle the athlete releases the ball
velocity of release - the velocity at which the athlete releases the ball

40
Q

define turbulent flow

A

the flow in which the velocity at any point varies erratically

41
Q

what effect does turbulent flow have on boundary layer separation

A

later boundary layer separation, less pressure

42
Q

define laminar flow

A

a type of fluid flow in which fluid moves smoothly in individual layers or streams.

43
Q

what effect does laminar flow have on boundary layer separation

A

earlier boundary layer separation, more pressure

44
Q

why does a golf ball with dimples travel faster

A

the dimples allow the turbulent flow to get “Stuck” behind the ball, allowing for less pressure to be exerted upon the ball, therefore having a greater velocity due to less drag.

45
Q

define form drag

A

the resistance created by the pressure differential on the front and back of an object moving through fluid.

46
Q

how can we decrease form drag

A

by becoming more streamlined by reducing the cross-sectional area.

47
Q

define surface drag

A

the friction between the fluid and the surface of the moving object.

48
Q

how can we decrease surface drag

A

wear swimming caps, lycra suits, shaving down

49
Q

define wave drag

A

the resistance 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 moves through water

50
Q

how can we decrease wave drag

A

improve buoyancy
make the object more streamline
improve technique of the swimmer

51
Q

define Bernoulli’s Principle

A

the velocity of the fluid flow determines the pressure system

52
Q

explain Bernoulli’s principle

A

the pressure on one side of an object is inversely proportional to the velocity on the same side of the object. as the velocity of the fluid increases, pressure decreases

53
Q

what is the Magnus effect?

A

a pressure differential occurs because the pressure is high on one side and low on the other, creating a lift, causing the ball to move in the direction of the pressure differential.

54
Q

why can a ball change flight path whilst it spins.

A

the Magnus force can change the flight path as pressure systems move from high to low.

55
Q

where do low pressure areas occur

A

airflow of spin goes in the same direction as there oncoming air.

56
Q

where do high pressure areas occur

A

airflow of spin goes against the direction of oncoming air.

57
Q

how does lift (Magnus force) occur

A

when high pressure systems move to low pressure systems.

58
Q

what does backspin ensure

A

maximum distance can be travelled

59
Q

what is the flight path of an object with backspin

A

ball holds longer in the air

60
Q

a ball is thrown with backspin, where is the low pressure and high pressure systems?

A

LP - top
HP - below

61
Q

what is the flightpath of an object with topspin

A

ball dips early

62
Q

a ball is thrown with topspin, where is the low pressure and high pressure systems?

A

LP - below
HP - top

63
Q

what does top spin allow

A

a ball to be hit/thrown harder with a higher velocity

64
Q

describe the airflow on a ball with side spin.

A

air moves from high to low pressure causing the ball to move in the same direction, creating lift, as the air moves from high to low, the curving of a ball occurs.

pes yr 12 (1 decks)

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