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Sport Biomechanics > Sport Biomechanics > Flashcards

Sport Biomechanics Flashcards

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1
Q

Angular velocity

A

angular velocity/ time

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2
Q

angular acceleration

A

change in angular velocity/ time

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3
Q

moment of inertia

A

mass x distance^2

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4
Q

angular momentum

A

moment of inertia x angular velocity

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5
Q

torque

A

moment of inertia x angular acceleration

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6
Q

angular impulse

A

torque x time = change in angular momentum

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7
Q

Kinetic Energy

A

1/2 x moment of inertia x angular velocity^2

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8
Q

arc length

A

radius x angle

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9
Q

tangential velocity

A

radius x angular velocity

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10
Q

tangential acceleration

A

radius x angular acceleration

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11
Q

radial acceleration

A

radius x angular velocity ^2 or v^2/r

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12
Q

SUVAT Equations

A 
v= u +at
v^2= u^2 +2as
s= ut + 1/2 at^2
s= 1/2 (u+v) x t
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13
Q

Newtons 1st law

A

An object either is at rest or moving with constant momentum unless acted upon by an external force

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14
Q

Newtons 2nd law

A

The sum of the forces on an object is equal to the total mass of that object multiplied by the acceleration F=ma. Also rate of change of momentum is proportional to the force.

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15
Q

Newtons 3rd law

A

When one body exerts a force on a second body, the second body simultaneously exerts an equal and opposite force back

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16
Q

Friction

A

= coefficient of friction x normal reaction force

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17
Q

Gravity Force Equation

A

Force= (G x m1 xm2)/radius ^2

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18
Q

Moments

A

= force x perpendicular distance

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19
Q

Scaler and examples

A

Magnitude- mass, time, speed

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20
Q

Vector and examples

A

magnitude and direction- weight, displacement, velocity and aceleration

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21
Q

Define Inertia

A

Reluctance of a body to change its state of moment.
High inertia= difficult to move, change shape.
Large mass = large inertia

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22
Q

what are the 2 types of movement and define

A 
Linear motion (translation) and angular motion (rotation)
Linear motion= when the centre of mass is moving
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23
Q

Difference between distance and displacement

A

Distance is the total distance travelled whereas displacement is the shortest route from the start to the end, it’s found using Pythagoras and will have a x and y component so can be written as a vector.

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24
Q

What don’t we call acceleration

A

Deceleration- always call it positive or negative acceleration

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25
Q

What does a standard 50Hz mean

A

In video, you’re taking 50 pictures every second

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26
Q

Whats a high speed video

A

you’re taking more than 50 pictures a second

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27
Q

How does a Charge coupled device work

A

There’s a chip which has diodes on it that are light sensitive. When light comes through, it hits the photocytes and produces a small charge. Light falls all over the chip and the chip measures the amount of light that’s fallen on each pixel. Then it sends the information to the computer so we know how much light has hit the chip in total

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28
Q

what are the 2 ways a charge coupled device could see a coloured image

A

1) . Use 3 chips so when light enters the front of the camera it gets split by a prism and is aimed at 3 different chips with a filter on. Have a red, green and blue components, then when you know hoe much light s hitting each component you put it together to get a coloured image.
2) . Can use a single chip which has a different filters over light sensitive diodes on chip (known as Bayer filter). There’s more green filters because the human eye is more sensitive to green.

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29
Q

Field of view

A

Make sure the field of view contains all the action you’re interested in

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30
Q

Focal length

A

Distance from sensor at the back TO the lens at the front

By varying this it changes the filed of view, its like zooming in

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31
Q

what does a small or large focal length mean

A

small focal length means a wide field of view

large focal length means a not as wide field of view

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32
Q

why should u avoid autofocus

A

Because when u start moving it will try and refocus the camera.
can autofocus to begin with but then turn it to manual

33
Q

whats shutter speed and what doenst it affect

A

shutter speed varys the time the sensor is exposed to light

It doesn’t affect the number of frames per second

34
Q

what happens if the shutter speed isn’t optimal

A

If shutter is open too long then it creates a blurry image.
However if its not open long enough, then not enough light will get In so it will be a dark image.
In this case you can additional lighting to brighten the image.

35
Q

Define centre of mass

A

a conceptual point, that can be real or fictitious, where all the mass of a body can be considered to be concentrated.
Its not a real point so you cant weigh or touch it

36
Q

How does motion occur in respect to CoM

A

The resultant force must pass through the CoM, if the CoM isn’t on the body then the projection of where the force is acting must pass through the CoM.

37
Q

Describe Gravity

A

Gravity is the force that acts between 2 masses. Its attractive and depends on the size of the masses and their separation

38
Q

Define centre of gravity

A

Conceptual point which would have the same potential energy of the body and through which the resultant gravitational forces will pass

39
Q

characteristics of a system being in equilibrium

A

sum of forces on body = 0

sum of moments about a point = 0

40
Q

What does the balance method do

A

It uses moments to calculate the centre of gravity

41
Q

Equipment for determining CoG and equation

A

Statograph- a device for finding the CoG by summing moments about one axis
Reaction Board- sums moments about 2 axis
total weight x total distance = (board weight x CoM of board distance) + (persons weight x CoM of persons distance)

42
Q

Whats the segmental method

A

Take moments along a line in components and then add them together and then use this to the find the overall CoG of the whole line.

43
Q

Define stability

A

the tendency of a body to remain or return to its initial position following the application of a force.
Stability can be passive or dynamic

44
Q

what does passive stability depend on?

A
  • weight
  • area of the base
  • horizontal distance of the CoG to pivot point, the greater the distance, the more effort to become stable
  • height of CoG above the base
45
Q

Potential energy when stable

A

Potential energy is at a minimum when equilibrium is stable.

Work must be done to move an object out of equilibrium and it has a tendency to return back to normal position

46
Q

Potential energy when unstable

A

Potential energy is a or near a maximum.
Very little or any work must be done to change this, any small movement will cause it to change position and become more stable

47
Q

Whats neutral equilibrium

A

Its an odd situation where an object moved but theres n change in the CoG position.
Works in symmetrical objects and the base of support is small

48
Q

When are humans passively stable

A

only when theyre lying flat

49
Q

how can people become more stable

A

use crutches/rods/guy ropes but moving around is still hard
or can use a skateboard, dynamic stability
humans need to use muscular force to remain balanced

50
Q

common reflex balance mechanisms

A

ankle strategy
hip strategy
stepping response
arm circle

51
Q

define force

A

a force of 1N is the force that will produce an acceleration of 1ms^-2 on a 1kg mass

52
Q

Whats polar form

A

having an angle and a magnitude

53
Q

how do u rearrange equations to show impulse = change in momentum

A 
impulse = ft
f=ma
a=(v-u)/t
f=m(v-u)/t
ft=mv-mu
54
Q

How do u find impulse on a graph

A

its the area under the graph, calculate it using the trapezium rule

55
Q

requirements for impulse

A
  • must know intial conditions
  • apply to x,y,z directions
  • must be net force
56
Q

how do u measure force

A

use a force plate

57
Q

describe how force plate works

A

has 4 transducers, one in each corner, these change state depending on how much force is applied to them so in each one measures the force in their corner and then the forces are summed.
gives info about the 3 planes

58
Q

does air resistance matter

A

not in calculations

but yes in real life it does especially with lighter objects

59
Q

shape of projectile motion

A

parabola

60
Q

where/how deoes gravity act

A

only acts in the vertical direction, the horizontal component = 0
so by taking regular time intervals, the size of the vertical gaps will increase while horizontal gaps remain the same

61
Q

what effects the range of a projectile

A
  • release velocity, faster u throw, the further it goes
  • release angle- if throwing and landing height r the same optimum angle = 45 otherwise its just less
  • height og release
62
Q

how do u solve a projectile problem

A

1) . divide into horizontal and vertical components
2) . see if u can solve for either vertical or horizontal with info given to u
3) . apply SUVAT to get unknown
4) . solve for other component and check it makes snese

63
Q

tricks in projectile motion

A
  • top of the parabola vertical velocity =o
  • if ends and start same place, displacement =0
  • if symmetrical then same displacement on the way up and down, can split it in half
64
Q

how do u throw for max distance

A

use max velocity and the optimum release height and angle are dependent on a persons physical characteristics
As release height increases, optimum angle decreases

65
Q

define motor control

A

=study of how movement is controlled

-ability to regulate or direct mechanisms essential to movement

66
Q

whast the process to get a response

A

stimulus=processing=response

in processing theres stimulus identification- response selection- response programming

67
Q

when does a somersault speed up

A

when it goes from the tucked to straight position

68
Q

mechanical principle in rotation

A

-angular rotation, it must be conserved

69
Q

key points of moment of inertia

A
  • rotational equivalence to mass
  • resistance of a body to change its state of angular motion
  • measure distribution about an axis
  • 3 axis, = lateral, longitudinal and frontal
70
Q

which poritions have most inertia

A

straight=large inertia, smaller angular velocity
pike = middle one
tucked= small inertia, large velocity

71
Q

equation for momentum in free fall

A

momentum is conserved

IsWs=ItWt

72
Q

how can u combat roational movement to conserve angular momentum

A

swing arms the opposite way to the way youre rotating

easier in tucked position as inertia is smaller so esier to create movement

73
Q

how can u change angular momentum

A

by an external force acting on it

74
Q

what positions does a force acting cause rotation

A

wont rotate if force acts through the centre of mass
but by force being opposite to direction of rotation causes rotation
swing arms forward to stop rotating forward

75
Q

whats aperture

A

size of the hole at the front of the camera

reffered to as f/stop number and its the ratio of focal length to aperture diameter

76
Q

meaning of small and large f/stop

A

small f/stop= larger the hole, larger aperture, mall depth of field, small shutter speed
large f/stop= small hole, small aperture, large depth of field, large shutter speed

77
Q

what do u need for 2d analysis

A

a camera
plane of movement
place camera perpendicular to movement plane
record scale info

78
Q

scale info

A

put an object of known dimensions in plane of movement
digitise object
calculate scale factor(done by dividing pixels/meters)
avoid perspective and parallax error

79
Q

perspective and parallax error

A

move camera further away to minimise persectve error

parallax error dpeneds where u place your headso reduce parallax error by placing camera perpendicular to movement

Sport Biomechanics (1 decks)

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