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SPORT TECHNOLOGY > SPORT MECHANICS > Flashcards

SPORT MECHANICS Flashcards

1
Q

Define Biomechanics, Kinesiology and Mechanics

A

Biomechanics= Bio (life). Therefore how a living thing produces movement.

Kinesiology= The study of movement.

Mechanics= The study of motion in space and time.

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2
Q

What is the difference between Kinetics and Kinematics?

A

Kinetics is how motion is caused. What is the cause of this? Therefore what forces have allowed the object/subject to move.

Whereas Kinematics is a mathematical description of motion.

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3
Q

Define Dynamics

A

The study of motion in contexts of ‘unbalanced forces’

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4
Q

Define Statics

A

The study of motion in contexts of ‘balanced’ forced.

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5
Q

Why not run barefoot?

A
  • Why not run barefoot?Scientists have debated the importance of footwear in running. The argument is that trainers disrupt our natural running style.In traditional running shoes athletes generally land with a traditional heel strike and the centre of pressure path (where you are applying the most force) will happen at the base of the heel and through the mid-line of the foot.Barefoot running will change the way that you run going from a heel foot striker to a mid foot striker. The centre of pressure path will start in the mid region of the foot and will move forwards into the forefoot region.To conclude those who run in trainers generally hit the ground with their heels first. Those who run barefoot generally hit the ground mid foot first.studies demonstrate that landing on your forefoot is the most effective landing style because it enables the arch in the foot to act as a natural shock absorber.When heel strike happens with trainers this causes the leg to become locked (when kicked forward) creating a straight line up the leg for the impact with the ground to travel through every joint resulting in hip,leg back knee etc problems. This way also produces more shock through the body than the natural way (even though there is no artificial padding).Also when you land the natural way less of your body comes to a dead stop.This is because the body has built in natural shock absorber that would accommodate to barefoot running if the athlete had trained this way for the majority of their lives. Distance athlete Zola Budd was famous for this.
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6
Q

Coincident centre of mass

A

When the centre of mass lies within the middle in one place.

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7
Q

The Centre of Percussion

A

If the axis of rotation is about the 2/3rds mark then it will have the same period. The centre of percussion which has a very special property.

Therefore on a racket if the ball engages the bat at the centre of percussion then nos ting is felt by the hand.

define impulse- Impulse is the change of momentum of an object when the object is acted upon by a force for an interval of time.

Therefore some time ago the sweet spot would be located in the throat of the wooden racket. Therefore, you could never hit it and expect good results. So by lowering the racket frame into the throat area (past the centre of percussion so now the centre of percussion was included on the base of the racket spring) players could now hit the centre of percussion. Effectively, at this point the translation and rotation add together so that the handle doesn’t move and the hand feels very little impulse(/jarring). If a ball is hit transversely to the bar at that place “the hinge feels no reaction.

But this was all patented so Head basically patented science. (The Prince Classic rackets).

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8
Q

air canon and sprite

A

Wider reading -Steve hake book

When a ball hits a racket:

  • 1st- it will push against it which will make the racket go backwards. This is called a translation.
  • 2nd- it will make the racket rotate about it’s centre of mass which will never located somewhere about the middle of the ball.

There is a point located on the racket to where you can hit the racket whereby the translation and rotation combine together so that consequently the handle does not move and thus the hand feels very little impulse.

This is known as the CENTRE OF PERCUSSION.

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9
Q

The Centre of Percussion

A

If the axis of rotation is about the 2/3rds mark then it will have the same period. The centre of percussion which has a very special property.

Therefore on a racket if the ball engages the bat at the centre of percussion then nos ting is felt by the hand.

define impulse- Impulse is the change of momentum of an object when the object is acted upon by a force for an interval of time.

Therefore some time ago the sweet spot would be located in the throat of the wooden racket. Therefore, you could never hit it and expect good results. So by lowering the racket frame into the throat area (past the centre of percussion so now the centre of percussion was included on the base of the racket spring) players could now hit the centre of percussion. Effectively, at this point the translation and rotation add together so that the handle doesn’t move and the hand feels very little impulse(/jarring). If a ball is hit transversely to the bar at that place “the hinge feels no reaction.

But this was all patented so Head basically patented science. (The Prince Classic rackets).

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10
Q

Define CoR

A

CoR is the ratio of relative velocity after and before and impact between two bodies.
Therefore essentially, velocity is taken prior to the impact and then taken after. This will help to determine simply how “bouncy” an object is

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11
Q

State the equation for CoR

A

CoR(e)= Relative velocity after collision (DIVIDED BY) Relative velocity before collision.

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12
Q

What does the e stand for in CoR(e)

A

The e is just a representation for what the CoR is equal to

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13
Q

CoR(e) when e=0?

A

This is a perfectly inelastic collision

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14
Q

CoR(e) When e=1?

A

This is a perfectly elastic collision. Therefore, velocity will bounce off with the exact same return.

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15
Q

What would you then describe as a real world inelastic collision range?

AND WHY?

A

0

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16
Q

When do we want to maximise CoR?

A

This will aid the athletes performance of that technique in most sports by making the action more efficient.

E.g.When bouncing a Basketball, we want to maximise the bounce to ensure that a tight grip and handle on the ball is achieved.

Also in Football, when kicking the ball to score we want to ensure that as much velocity on the ball is translated from the initial kick by the athlete.

In tennis, when performing a serve we want the ball to have the characteristics to allow the maximum amount of velocity to be translated into the serve that has been generated in the serve. This is all object to object impact so there are an array of examples in other sports e.g. Hockey, Cricket, Baseball where the same purpose lies.

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17
Q

When do we want to minimise CoR?

A

This will be when the velocity of the impact will be absorbed. In Gymnastics e.g. crashmats, this is to achieve a sharp landing, the ground will absorb much of the velocity upon the collision.

Also takes place in ice Hockey, boxing.

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18
Q

What is the equation for CoF?

A

F=mue times F(n)

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19
Q

When do we want to maximise CoF

A

Where there needs to be some traction between the two objects in order to provide a gripping effect.

E.g. Running trainers, Athletic shoes, spoils of F1 cars, cycling when turning corners around the velodrome ( it is the Bernoulli principle that aids with this).

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20
Q

When do we want to minimise the CoF?

A

Skeleton Bobsleigh, Ice Skating and Ice hockey.

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21
Q

What is an industry application to the regulation of CoR/CoF.

A

Air Canon/ (now) Sprite with the ITF

22
Q

Explain why the camera should be set up at half the height of the activity

A

Allowing for any expected movement of the participant to be captured

23
Q
  • Why is it important to make minimal errors in the recording stage.
A

Errors made in the recording stage can often not be recovered later on and can lead to useless data.

24
Q
  • Describe the general steps of Camera set up and provide examples.
A

Set up the trtipod and level it.

The Camera lens hegith would normally be set up at half of the activity so this allows for any unexpected movement of the participant. 

position camera on tripod, this is important to avoid **tilt, and roll motion** occurring. This would be the incorrect positioning of the camera on the Tripod base causing a forwards or backwards tilt of the camera. This would affect focus of the camera, calibration of the camera (only distances), the camera person's ability to pan (moving the camera from left to right). 

Ensure that the camera is perpendicular to the activity or **Field of view.** 

So when measuring **Spatio-temporal parameters** such as step frequency and stride length if we are unable to pan accurately (smoothly) to capture data due to tilt and roll errors in the camera view then this will inform errors in the recording stage that will consequently cause our raw data to be inaccurate and useless.   **** 

Ensure that the camera view is level e.g. tilt and roll.
25
Q

Describe the general points regarding Camera Settings

A

Manual focus is IMPORTANT. You need to focus the camera on the object that you will be capturing (or in the space that you will be capturing). If you don’t endure this process then when your camera is set on the background of your activity and the athlete enters the Field of View at the speed of the pronounced activity, for example an athlete sprinting 50m into a camera Field of view set in a zone of 20-30m. Then the Camera (A basic C.) would not be able to focus quickly enough between the image of the background of the activity and the athlete entering the frame. Therefore, we need to zoom onto an object exactly where the activity will be taking place, as far as possible and allow the camera to focus, and then zoom out.

Shutter speed has to be appropritate otherwise if it has a low shutter speed then it is likely to freeze the motion. We want a smooth image and this needs to be defined the msot because it will affect the others below. After we then define the Iris, if we do not define the Iris/ electronic gain then we obtain motion blur. When we define the Iris to be very low for example 1/500 (=we want it open), then this does not allow for much lighting. As a result we change the Acpunture to account for that.

-sharp image.

Additionally, there needs to a judgement called on the external lighting conditions (in the room/ environment), as well as different places in that room (environment) whereby the lighting intensities may differ.

26
Q

Describe the general points regarding accuracy during Video Recording

A

There needs to be a calibration object to record scaling information. This is so that there is an object that has been in the Field of View where we have knowledge of it’s real life measurement. Therefore, we can relate this to the axis used when we apply a programme to analyse our data, so that we can generate accurate information to scale.

Ensure that during the recording of the movement trial, the camera does not move after the calibration has been recorded.

27
Q

Define the term kinematics

A

Kinematics is the description of motion. (It has two strands Linear Kinematics and Angula kinematics).

28
Q

Describe the different forms of motion.

A
  1. Motion can be classified as Linear motion. This can be split up into rectillinear motion and curvillinear motion.
  2. Motion can be classified as angular motion (rotation).
29
Q

Define scalar

A

(of a quantity) Having only magnitude, not direction

30
Q

Define vector

A

A quantity having direction as well as magnitude

31
Q

State and define the kinematic parameters (6)

A

All of the below parameters have both linear and angular definitions.

First we have to define:

Position-
In order to understand how something has moved (motion) then we have to define and understand its position and how this has changed.

Position-
The position of an object refers to its location in space relative to some baseline value or axis.

Distance- Length of path which a body covers during motion. units m. Note that displacement is a scalar.

Displacement-
Note that displacement is a vector variable.

The change in position of a body during motion.
Length of the ‘straight line’ path from initial to final position and includes the specification of the direction.
units (metre/m)

Speed-
Is the rate of change of distance and is a scalar quantity.

Velocity-
This is the rate of change of displacement and is a vector quantity. How quickly an object moves from its initial position to it’s final position. Velocity is a vector quantity.

Acceleration-
Acceleration is a vector quantity that is defined as the rate at which an object changes its velocity.

32
Q

Explain the process we endure prior to considering any parameters.

A
  1. Define position e.g. coordinate data (x,y)= the Cartesian coordinate system.
  2. Then before any kinematic analysis we need to define the spatial reference system.
  3. And then note that every coordinate plotted on a graph can be described by a position vector
33
Q

Define position vector.

A

A position vector has components in the x and y directions

34
Q

Exam question Linear kinematics 1

A

A ball was kicked with a horizontal velocity of 10m/s and vertical velocity of 5 m/s. Calculate the resultant velocity of the ball at take off.

35
Q
  • Wider reading prior to EIS data collection workshop. 29/10/2019
A

Hay 1993, defines maximal velocity sprinting as the product of step frequency (or step rate) and step length. So in order to acheive maximum sprinting velocity the optimum combination of SL and SF must be achieved.

Therefore, we must define the following:

A step is defined as the distance between successive points of contact of the opposite feet.

A stride is defined as the distance between successive points of contact of the same foot and subsequently a stride is the sum of two consecutive steps.
36
Q

Define aperture

A

The mount of light that enters the camera

37
Q

Define the Centre of gravity

A

The imaginary point about which an object’s mass is equally distributed.

38
Q

Define the Centre of Mass

A

The imaginary point about which an object’s mass is equally distributed.

39
Q

Explain why we can assume that the position of Cof M and Cof G are identical

A

Because the strength of gravity at the top of the object is similar to the strength of gravitational pull at the bottom of the object. This means that the centre of mass lies in the same position as the centre of gravity

40
Q

State the easiest way to locate the Cof G on simple rigid objects

A

You will need to locate the balance point or the pivot. To find the balance point mathematically you will have to identify the point where the turning effects (moment/torque) of forces sum to zero

41
Q

Define torque and define it’s equation

A

(A moment) A force that causes rotation- it is the angular equivalent of force.

Moment= Force x distance

Units= Newton x meters= Nm (Newton meters)

A moment produces angular acceleration.

42
Q

Explain how the Cof G in the Human body is not fixed

A

When standing in the anatomical position the “average” position of the Cof G is:

Male= 57% of standing height.

Female= 55% of standing height.

But by moving body segments and redistributing the mass, the Cof G will also move.

43
Q

State the three factors that determine an objects stability

A
  • The area of the base and the relative position of the line of gravity within the base.
  • The height of the centre of gravity above the base.
  • The mass of the object
44
Q

Describe the inverse relationship between Mobility and Stability

A
  • Often in sport it is necessary to alter stability intentionally to become mobile.
  • To be mobile, the C of G should be as close to the edge of the base of support.
  • Ability to start, stop and change direction requires an ability to manipulate stability.
45
Q

What unit is essential to use when comparing the relationship between Linear and angular motion?

A

RADIANS

46
Q

What is linear displacement the product of.

A

Radius and angular displacement.

47
Q

Torque

A

Turning effect of force , change in orientation, moves our limbs

48
Q

Centric Force

A

Does not create torque, center of gravity, causes linear motion

49
Q

Eccentric Force

A

Not through the center of gravity (non-centric)
Causes linear and angular motion
NOT describing muscle action

50
Q

SI Unit for Torque

A

SI unit is N·m

51
Q

Center of Gravity

A

The COG is the point in a body or system around which its mass or weight is evenly distributed or balanced and through which the force of gravity acts.
If you stand on your tip-toes, your COG is elevated
If you squat down, your COG is lowered

52
Q

Who has a lower COG between men and women?

A

Women usually have lower COG (~55% of height) compared to men

SPORT TECHNOLOGY (7 decks)

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