Revision session info Flashcards
Newtons Law of Inertia
an object either remains at rest or continues to move with constant momentum, unless acted upon by a net force
Newtons Law of acceleration
the rate of change of momentum of a body is proportional to the force causing it and the change takes place in the direction in which the force acts
Centre of mass
the conceptual point where all the mass of a body can be considered to be concentrated
Newtons law of Reaction
for every action force there is a reaction force which is equal in magnitude but opposite in direction
“every action has an equal and opposite reaction”
Longitudal axis
Up and down
Transverse axis
Left and right
frontal Axis
Front & Back
Vertical Average Loading rade (VALR)
average gradient between 20-80% of impact peak
Verticle Instanteneous Loading Rate
maximum gradient before impact peak
Embedded force platform pros
accurate and reliable 3D force measurements
high sampling frequency and resolution
Embedded force platform cons
often restricted to indoor use and a single step
possibly unnatural gait (force plate targeting)
Projectile motion
Splitting motion into vertical and horizontal components
Portable Force monitors pros
Portable force monitors can be used outside of a lab setting, making them more versatile.
They provide a good alternative when fixed force plates are not available or practical.
Portable force monitors cons
UP
Typically, they are less accurate and reliable compared to lab-based force plates.
Often only measure vertical forces.
May not be embedded into the ground, which can affect the accuracy of certain movements (e.g., running over a raised surface).
Triaxial accelerometer
measures instantaneous acceleration
at rest will measure 1g due to gravity
orientation is important
Triaxial Accelerometer Pros
Can be cheaper and easier to use compared to other force measurement tools.
Often embedded within other devices such as GPS units, making them multifunctional.
Measure acceleration in three dimensions (x, y, and z axes), providing comprehensive data on movement.
Triaxial Accelerometers Considerations
PMB
Placement: The position where the accelerometer is placed on the body or equipment can affect the measurements. For example, a GPS unit with an embedded accelerometer might not accurately represent the centre of mass.
Movement Influence: The presence of the device should not interfere with the natural movement of the subject.
Battery Life and Comfort: Ensure the device has sufficient battery life for the duration of the measurement and is comfortable for the user to wear.
Accelerometer pros
price, easy, embed
cheaper than lab equipment
easy to use
often embedded within other devices
can monitor closer to the site of interest
Accelerometer cons
valid for intended purpose?
affect the movement being monitored?
battery life,
Frame rate vs Shutter speed
Frame Rate
Definition: The number of frames (or images) captured per second in a video.
Units: Typically measured in frames per second (fps) or Hertz (Hz).
Shutter Speed
Definition: The length of time the camera’s shutter is open to expose light onto the camera sensor for each frame.
Units: Typically measured in fractions of a second (e.g., 1/50 s, 1/1000 s).
Focal Length
Definition: The distance between the camera lens and the image sensor when the subject is in focus.
Short Focal Length
Wide-angle view, captures more of the scene, often used for landscapes.
Long Focal Length
Narrow field of view, magnifies distant subjects, often used for wildlife or sports photography.
Depth of field
The range of distance within a photo that appears acceptably sharp and in focus.
Lens Distortion
The alteration of straight lines and shapes in an image due to the design of the lens.
Barrel Distortion
Lines bow outward from the center of the image. Common in wide-angle lenses.
Pincushion distortion
Lines bow inward toward the center of the image. Common in telephoto lenses.
Mustache Distortion
A complex combination of barrel and pincushion distortion
How to measure scale info
MeasuredLength(inpixels) ÷ KnownLength(inrealunits)
CoG
Centre of Gravity (CoG)
Definition: The Centre of Gravity (CoG) is the point at which the entire weight of an object or body is considered to be concentrated and where the force of gravity acts. It is the balance point of the body.
Balance
the ability to maintain the body’s centre of mass over its base of support, whether stationary (static balance) or moving (dynamic balance).
Passive Stability factors
GM, LB, LCG, FD
Greater Mass: More inertia, harder to move.
Larger Base of Support: Increased stability.
Lower Center of Gravity: More stability, less likely to topple.
Further Distance from Pivot: Increased torque needed to tip over.
stable equilibrium
Potential energy at a minimum
Work must be done to change
Tendency to return to original posture
Unstable Equilibrium
Potential energy at or near a maximum
very little if any work must be done to change
small movement takes the gravity line the base
Neutral Equilibrium
Object moves but no change in potential energy
based of support is small but doesnt matter
Modifiable factors to increase stability
keeping CoG over base of support
lowering CoG
increasing mass
extend base of support towards oncoming force
shift CoG towards oncoming
Common reflex balance mechanism
Ankle Strategy
Hip Strategy
Stepping response
Arm circle
increasing response to severity of perturbation and safety constraints
Friction
a force that acts in opposition to the movement of one surface over another
Normal Force
is perpendicular to the surface in contact
mass * gravity
Relative Velocity
Headwind or tailwind
the total velocity
velocities in oppositve direction: sum
Velocities in same direction: difference
Laminar Flow
Fluids slide smoothly over
layers flow in parallel
little disruption to fluid
Turbulent flow
order, slow, streamline
Less orderly
Greater impact on object slowing it down
boundary layer is composed of vorticies that increase surface friction creating more disruptiob
common at the rear of non-streamlined objects
Reducing drag
More Streamlined shap
Smaller surface area
Constraints to movement: Movement Pattern
A general series of anatomical movements that have common elements of special configuration.
Constraints to movement: Skill
When a general movement pattern is adapted to the particular constrains of a particular task it is called skill.
Constraints to movement: Technique
When a particular type of the same skill or task is performed, it is called a technique
Constraints to movement: Style
how an athlete performs it
Within each technique a performer may use individual modifications (e.g. individual timing). This is defined as the style of performance.
Constraints to movement: Rules and Environment
Rules may guide / penalise natural movement (i.e. follow-through after discus throw)
Constraints to movement: Human Factors
Strength, Power, Speed, Flexibility
