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Atar Physed > Biomechanics > Flashcards

Biomechanics Flashcards

1
Q

What is biomechanics

A

the study of motion and the effects of forces relative to the body
applied to the laws of mechanics and physics to human performance
- contributed to the improvement in mechanical aspects of sport performance

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2
Q

Benefits of biomechanics

A
  • technique efficiency
  • injury reduction through an understanding of injury causes and application of correct technique
  • modification of sports equipment to improve sports performance at all levels
    E.g. younger - lighter
  • technological development of equipment and computer technology to assist in transition from practise field to playing field
    E.g. bowling machine in cricket
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3
Q

Types of motion

A
  • definition of linear motion and how it applies to a selected sport
  • definition of angular motion and how it applies to a selected sport in relation to angular velocity
  • definition of general motion and how it applies to a selected sport
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4
Q

Motion

A
  • movement that occurs when an object has changed positions in space and in time, due to application of forces
  • for motion to occur, a force must be applied to that object. This force can either be an;
    Internal force
  • structures of the body’s that interact to produce movement
  • e.g. action of muscles and tendons that act together to produce forces that cause movement
    External force
  • result from the interaction between the body and the environment. These can include contact forces and non contact forces
  • gravity
  • friction
  • air resistance
  • water resistance
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5
Q

Linear motion

A
  • where movement is along a straight line, there is no rotation and all body parts move in the same direction at the same time
  • also referred to as translation - where a body experiences translation, it moves as a unit, portions of the body do not move relative to each other
  • e.g. an ice skater gliding after they completed a movement or a cyclist who stops pedalling
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6
Q

Rectilinear motion

A
  • movement is linear and occurs through a straight line
  • this is often represented by the body as a whole or certain point of the body (the head when running)
  • a basketball chest pass or baseball pitch are good examples where the balls path is flat and in a straight line
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7
Q

Curvilinear motion

A
  • movement is linear but object moves through a curved trajectory
  • think about the pathway of a ball during a shot on goal in netball or the flight path of long distance ski jumper
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8
Q

Angular motion

A
  • where all parts of the body move through a rotational pathway, through the same angle, in the same direction and at the same time
  • it is the rotary movement about an axis
  • as a result, all body parts do not move through the same distance
  • when objects move through an angular pathway, all body parts do not move through the same angular distance with the most distal point covering the greatest distance
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9
Q

General motion

A
  • combination of linear and angular motion
  • human movement usually consists of general motion rather than pure linear motion of angular motion. This is a result of the angular rotation of a number of body segmented combining to produce linear motion of the body
  • e.g. a cyclist may move in a straight line as a result of the rotation of the legs about the hip joint
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10
Q

Describing and measuring types of motion

A

Linear motion and how it applies to a selected sport in relation to;
- speed
- velocity
- acceleration
- instantaneous measure/mean measure

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11
Q

Distance

A
  • Refers to how far you have travelled from your start to finish position
  • measure in terms of total distance covered
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12
Q

Displacement

A
  • Measures the overall change in position of a person and is measured in magnitude and direction
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13
Q

Linear motion - speed
Speed

A
  • Measure of the distance an object travels per unit of time
  • representative of how quickly you cover a given distance
  • calculated by dividing distance travelled by time taken
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14
Q

Linear motion - speed
Types of speed

A

It is important to be able to determine the different types of speed as collectively they provide critical information relating to different aspects of turn events
i.e. Average speed for the entire race does not tell us what went on during the race itself
- does not tell us the max speed reached by the racer
- does not indicate when the race was speeding up or slowing down

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15
Q

Linear motion - velocity

A
  • Speed in a given direction
  • calculated by dividing displacement travelled by time taken
  • A change in velocity could be representative of a change in speed, change in direction, or both
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16
Q

Linear motion - acceleration

A

Rates at which the velocity changes with respect to time
- positive acceleration: velocity is increasing
- negative acceleration (retardation): velocity is decreasing
- zero acceleration: no change in velocity

17
Q

Acceleration due to gravity

A
  • Naturally occurring force resulting in downward acceleration on a body at constant rate at 9.8m/s
    -this closely elated to another term known as uniform acceleration
18
Q

Uniform acceleration

A
  • When a body accelerated at a constant rate in both magnitude and direction i.e. The acceleration is the same over time
  • gravity causes an object to accelerate at a constant rate of 9.8m/s making it uniform acceleration because it increases speed at a constant rate
19
Q

Angular speed/velocity

A
  • Angular speed is calculated by dividing angular distance by time
  • angular velocity is calculated by dividing angular displacement by time
  • in striking sports, to maximise angular velocity, athletes must find a way to maximise the angular displacement the implement moves through whilst minimising the time component
    As the distal end of level will always move through the greatest angular displacement, athletes typically try to maximise the length of the lever (extend at the arms) just prior to impact to maximise velocity impacted on the ball
20
Q

Force

A
  • force is the product of mass x acceleration, represented mathematically as F v ma
  • the concept f force is common to all newtons laws
  • force is any interaction (e.g. a push or pull) threat, when unstopped, will change the motion of an object, it is used to;
    1. Get objects moving
    2. Stop objects moving
    3. Change the direction f a moving object
    4. Change the speed of a moving object
    5. Balance another force to keep an object still
21
Q

Forces may be external

A
  • result from the interaction between the body and the environment, these can include contact forces and no contact forces
  • gravity
  • friction
  • air resistance
  • water resistance
22
Q

Forces can also be internal

A
  • structures of the body that interact to produce movement
  • e.g. action of muscles and tendons that act together to cause movement
23
Q

Types of external forces

A
  1. Contact forces
    - those forces that act on objects that come into direct contact with one another e.g.
    - friction forces
    - ground friction forces (GRF)
    - air resistance
    - water resistance
  2. Non contact forces
    - those factors that act on objects without coming into direct contact with one another
    E.g.
    - gravity
24
Q

Newtons 1st law of motion - INERTIA

A
  • “ a body continues in its state of rest or state of motion unless acted upon by a force.” This law is also referred to as the law of inertia
    Can be applied to
  • creating movement - golf ball remains in the tee unless force is exerted on it
  • changing movement - once hit, the ball would travel forever if no forces were acting on it to slow it down and bring it back to earth and stop it moving
  • air resistance is a force that slows the ball down
  • gravity is a force that pulls the ball back to the ground
  • friction is a force that stops the ball rolling
    Inertia describes the amount of resistance to a change in an objects state of motion
  • the greater an objects inertia, the greater the force required to initiate its movement or change its state of motion
  • is directionally proportional to an objects mass
    E.g. shot putt - large mass - large force needed to overcome inertia
25
Q

Newtons 2nd law of motion - acceleration

A

“The acceleration of a body is proportional to the force applied to it and inversely proportional to the mass of the object” this law is also referred to as the law of acceleration
- the greater the force applied to an object, the faster the acceleration will be
- if the same force is applied to the objects of differing mass, the object with less mass will accelerate faster
If the mass of the object is constant
- increase force = increased acceleration
- decrease force = decrease acceleration
If the force applied to the object is constant
- increase mass = decrease acceleration
- decrease mass = increase acceleration
Force = mass x acceleration
If the force is applied to two objects of different masses, the object with the lower mass accelerates faster
- for an object of a greater mass to accelerate at the same speed as an object of a lighter mass, the force applied to it must be greater than the force applied to the lighter object

26
Q

Momentum

A
  • a measure of the amount of motion a body mass has measured in Ns (newton seconds) by a body moving. It’s the product of mass and velocity
  • an object moving can only have momentum if it is moving
  • the greater its momentum, the more force that needs to be applied to either stop of slow the object down
  • as a result, when two bodies collide, the one with the most momentum will be at least affected
    P = mv
    P = momentum
    M = mass
    V = velocity
27
Q

Impulse

A
  • impulse is the application of ford over a period of time to change the momentum of an object
  • the concept of impulse and the impulse-momentum relationship is best described by the following formula:
    Impulse = force x time
  • when a force equals the objects mass multiplied by its acceleration, and time equals the length of time for which the force is applied to the object
    1. Impulse created momentum e.g. increases the momentum of an object from zero
    2. Changing momentum e.g. increasing / decreasing momentum of a moving object
    3. Stopping momentum e,g, taking momentum back to zero
    The longer the force can be applied, and the greater the force that is applied, the greater the objects impulse or change of momentum
    Impulse is importantly in impact / collision situations
  • we often want to manipulate the momentum of one of the colliding objects to produce a desired outcome
  • I.e. speed up or slow down an object
  • for example - the tennis racquet tension example
28
Q
  1. Increasing momentum
A
  • to maximise the momentum of an object, one must increase the force component
  • this occurs by the athlete demonstrating effective sequencing of movements (see sequential summation of force) and undertaking weight training programs to increase the cross sectional sea of muscles
29
Q
  1. Decreasing momentum
A
  • to reduce the momentum of an object, one typically looks to increase the time component
  • a cricket ball is hit towards a fielder. The fielder wishes to stop the ball (take momentum back to zero)
30
Q

Newtons 3rd law of motion

A
  • “ for every action, there is an equal and opposite reaction”
  • forces cannot act alone and must exist in pairs
  • when two objects exert a force upon each other, the forces are opposite in direction and equal in magnitude
  • when analysing newtons 3rd law, one of the forces involved is referred to as the ‘action’ whilst the other is referred to as the ‘reaction’
  • typically in sport, the athlete is responsible for creating the ‘action’
  • in passing in basketball, the athlete exerts an ‘action’ force on the ball in the downward direction
  • they ground then exerts an equal and opposite ‘reaction’ force on the ball causing it to bounce up into the hands of the receiving player
31
Q

Ground reaction forces (GRF)

A

In analysing movement, we look at ground reaction forces - that is, force exerted by the ground on a body in contact with it
- every time we make contact with the ground, it exerts an equal and opposite reaction force back on the body
- this is used to create movement when we walk - with each step we exert a force downward and backward and the ground exerts a reaction force upwards and forwards allowing us to move
- whilst the size of this force is only slightly bigger than our body weight (approx 1.2) when walking, it increases significantly with other activities such as sprinting (approx 3 body weight) and jumping (approx 8* body weight), potentially leading to injuries
- approximate recovery, training volumes and footwear must be considered to avoid such injuries

Atar Physed (6 decks)

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