Biomechanics Flashcards
Anatomical Position
Position where body is standing straight with the arms at its side and palms facing forward.
Body weight
The mass (amount of matter that makes up an object) and acceleration (due to gravity) of an object.
Linear motion
Refers to a motion along a line (trajectory or path of an object)
Angular motion
refers to the rotation of a whole body or segment (forearm or leg), or an implement (bat, stick or club) about a real or imaginary axis of rotation.
General motion
A combination of linear and angular motion.
Mass
The amount of matter that makes up an object
Inertia
The tendency to do nothing or remain unchanged
Momentum
The quantity of motion of a moving body, measured as a product of its mass and velocity
Impulse
Something that causes something to happen or happen more quickly
Acceleration
How quickly an object is changing its velocity
Calculated using velocity/time
Measured in m/s/s
Velocity
A measure of how long it takes you to travel a certain distance
Calculated using distance/time
Measured in m/s
Law 1
Inertia
A body will continue in its state of rest or uniform motion in a straight line, unless acted upon by an external force
Example of Inertia
A Tee-ball sitting on the tee will remain in that position unless acted upon by an external force (bat or wind). This is the creation of motion
Once hit the ball remain travelling in a straight line unless acted upon by an external force (air resistance, gravity). Air resistance reduces velocity, while gravity pulls the ball down. This is the change of motion
Law 2
Law of acceleration
Force is equal to mass ‘times’ acceleration
Example of the Law of Acceleration
If we want to change the acceleration of the tee-ball then we have two options (i) change the force applied (ii) change the mass of the ball. Given the mass of the ball is constant, then our only option is to change the force applied at impact
If you want the ball to go further, then you need to apply a greater force; you must swing the bat harder
Law 3
Action-reaction
For every force there is an equal but opposite reaction
Example of action-reaction
As the bat makes contact with the ball it is the force applied (F2-1) that causes the ball to fly into the air. The ball also applies an equal force back against the bat (F1-2) and this assist in bringing the bat to a stop and also why you feel the ’tingle’ in your hands as the bat vibrates following contact.
Rectilinear
Straight line
Curvilinear
Curved trajectory
Distance
The total distance, measured in metres, that you have travelled from your starting point.
Displacement
The change from overall starting position. Measured in metres, the difference between your staring point and finishing point in a straight line.
Projectile
A projectile is any object which once dropped or released continues in motion by its own mass and is influenced by downward forces of gravity.
Velocity of release
Refers to how fast the object is moving at the time of release
A higher release or take-off velocity will result in an increased horizontal or vertical displacement (depending on angle released)
Angle of release
Refers to the angle at which the object is released
The angle of release and velocity of release are directly linked. If you are wanting to jump vertically (HJ) you could approach with an ‘optimal’ velocity NOT with a ‘maximal’ velocity. However if your were wanting to jump horizontally you approach with a ‘maximal’ velocity.
Height of release
Refers to the height at which the object is released
to consider height of release we also need to look at the landing or finishing position.
Angular distance
How far the body segment or implement rotates from its starting point
Angular velocity
How quickly the body segment or implement rotates.
calculation is distance travelled / time taken
COG
an imaginary point, which my lie inside or outside the body, about which all of the body’s mass is equally distributed.
Base of support
area created by points of contact on the supporting surface
The larger the surface area the greater the balance, however we also need to consider the position of the cog
Line of gravity
An imaginary line that extends from the cog to the bos
A more stable position is created when the line of gravity falls within the middle of the bos.
Mass - stability
An object with a greater mass would be more difficult to move or change its current motion
A heavier object has more static balance than a lighter object
Height of cog
An object with a lower CoG is more stable than a higher CoG
Accuracy approach
When the task requires accuracy and the distance is not a problem; like a netball shot or darts throw.
The movement of required body segments occurs at the same time and thus this is referred to as ‘simultaneous summation of forces’
Whilst the final velocity is reduced, the accuracy is vastly improved.
Maximum velocity approach
When the task requires a high velocity at release or impact, accuracy is sacrificed to ensure maximal velocities can be achieved; hitting a baseball or teeing off in golf
The movement of required body segments occurs as the previous segment reaches its peak velocities, this is referred to as ‘sequential summation of forces.