The following definitions
and equations have been included within the blog to allow a novice learner in
the field of biomechanics a greater basic understanding of the terminology and
how they work.
Definitions
acceleration rate of change in velocity over the change in time
angular
acceleration rate
of change of angular velocity; equal to angular velocity per unit of time
angular
displacement change
in angular position or the orientation of a straight segment
angular
impulse product of torque and time (torque
produced over a period of time); equal to the change in angular momentum of an
object
angular
momentum product of the moment of inertia and
angular velocity; angular analogue of linear momentum
angular
velocity rate of change in angular
displacement; equal to angular displacement per unit time
axis
of rotation imaginary line passing through the
centre of rotation; perpendicular to the plane of rotation
biomechanics field of science devoted to understanding mechanical
principles in relation to biological organisms
centre
of gravity point about which the sum of torques
if all points weights (that is, mass × gravity) of a body equals
zero; the body can balance at this point
centre
of mass point about which the sum of torques
of all point weights of a body would be zero if oriented perpendicular to the
line of gravity
efficiency ratio of the input to output of a system; often refers
to ratio of energy in to energy out
force product of mass and
acceleration; induces a change in the mobile state of an object
impulse product of applied force and
the time over which it is applied
impulse-momentum
relationship relationship
between impulse and momentum; the momentum of an object will change in
proportion to the sum of applied impulses
inertia tendency for a body to remain
in its present state of motion
kinetic
chain linked
segments of a body that move together
linear straight or curved but not
circular (rotational) path
linear
acceleration rate of change of linear velocity;
equal to angular velocity per unit time
linear
displacement change
in linear position or the orientation of a straight segment
linear
momentum product
of the mass and linear displacement; equal to linear displacement per unit of
time
linear
velocity rate
of change in linear displacement; equal to linear displacement per unit time
mass quantity of matter in an object
moment
of inertia tendency
for a rotating body to remain in its present state of motion; equal to the
product of the mass if an object and its radius of gyration
moment
of force (torque) the result of a force acting at a
distance from a centre of rotation; rotational action of a force
Newton's
Law's
First: An object will remain at rest or continue
to move with constant velocity as long as the net force equals zero.
Second: The acceleration of an object
is proportional to the net force acting on it and inversely proportional to the
mass of the object.
Third: For every action, there is an
equal and opposite reaction.
power rate of doing work; work per
unit or the product of force and velocity
push-like
movement pattern pattern
of movement whereby the joints linked segments extend (or flex) simultaneously;
optimum pattern for high force and accuracy
radius
of gyration distance
from the axis of rotation to a point where the centre of mass of the object
could be located without altering its rotational characteristics
recovery
phase period during which an appendage is
repositioned from the back to the front of the boy in preparation for the swing
phase
rotation circular (non-linear) motion or motion about an axis
of rotation
speed rate of change of distance,
without reference to direction
swing
phase period during which an appendage is
repositioned from the front to the back of the body; usually associated with
the application of propulsive force
throw-like
movement pattern patter
of movement whereby the joints of linked segments extend (or flex) in a
sequential order, usually proximo-distally; optimum pattern for the attainment
of high movement speeds
trajectory flight path of a projectile
translation linear motion
Equations
speed Δd/Δt
velocity
(v) Δs/Δt
acceleration
(a) Δv/Δt
angular
velocity (ω) Δθ/Δt
angular
acceleration (α) Δω/Δt
or τ/I
force (F) m×a
torque
(moment of force) (τ) F×d, where d is the moment arm of
force, or τ = Iα
sum of
moments or sum of torque (ΣM or Στ) τt = τ1 + τ2 + τ3 ...
momentum
(M) m×v
angular
momentum (H or L) Iω or
mk²ω
angular
impulse-momentum relationship τ∙t = Iω
impulse
(J) F×t or Δmv
inertia m
moment
of inertia (I) Σmr² or
mk²
power
(P) F×v or W/t
All definitions and equations found in Blazevich's (2010) Sports Biomechanics.