Basic Biomechanical Definitions Flashcards
inertia
characteristic of a body/object that reflects the body’s propensity to resist changes in its state of motion.
It’s proportional to the body’s mass (when at rest) and momentum (when moving).
Force
mass X acceleration
May be described as a PUSH or PULL that speeds up, slows down, changes the direction of, or deforms an object.
weight
when objects acceleration is due to gravity
work
a force applied over a distance
force X distance
energy
the capacity to work
Power
work/time OR energy/time OR force X velocity
Rate of work production
sometimes described as explosive strength
Velocity/speed
distance covered in a given time
velocity also provides info about direction whereas speed doesn’t.
DISTANCE and TIME
acceleration
change in velocity in a given time.
It is always reported with the time in the denominator squared.
pressure
force/area
stress & strain
Stress is a special type of pressure, thus force/area.
Stress is the stimulus applied to a material such as bone or ligament.
Strain is the response of the material to the stress or pressure…measure of deformation.
Strain - deformation/original shape OR
change in length/original length
Muscular strength
maximum work one can accomplish in one attempt…at a given velocity
Muscular power
Strength (work) divided by time
S/T=P
Muscular endurance
Maximum work one can perform repeatedly.
Usually refers to work that is dependent upon anaerobic pathways for energy.
Rotary/angular movement
Circular movement that results from a force being exerted on a rigid link at some distance from an axis of rotation.
Angular displacement
a change in rotational position; most often measured in degrees
Angular velocity
angular displacement achieved in a given time.
Angular acceleration
change of angular velocity in a given time.
Torque/movement
Force X Lever arm.
Torque is the rotary effect of a force.
Lever arm/moment arm/torque arm/force arm/resistance arm
the perpendicular distance from the line of force to the axis of rotation - also the shortest distance if you think about it.
Lever 1
simple machine which consists of a RIGID BAR (bone) & a FULCRUM (axis of rotation or joint).
Lever 2
Muscular force (may also be gravitational) is exerted on the bone at some distance from the joint. In this situation we will have rotational movement, and torque is produced. Extremely common in human body. When performing an arm curl, we must ask as to the torque produced about the elbow and not force.
Impulse
force X time
changes in impulse are always proportional to changes in momentum
Momentum
mass X velocity
Linear movement
What creates more impulse…follow through or the start of the throwing motion and why is this important to know?
Follow through creates more impulse. Good technique for strength in rehab
angular momentum
moment of inertia X angular velocity
Moment of inertia is a reflection of how the mass is distributed about the axis of rotation - if mass is farther away from axis of rotation, moment of inertia is greater. If mass is tightly packed around axis of rotation, moment of inertia is small.
Common in gymnastics, diving, figure skating
Propulsive Force
Example: baseball catcher
move hand towards ball
Absorbed Force
Example: baseball catcher
move and away from ball
I=FxT
Impulse
Mechanical Advantage
ratio of effort arm to resistance arm.
EA/RA Less than 1 reflects relative disadvantage.
Effort arm is often called the…
Force arm
Rotational work
torque X angular displacement
T x AD
Rotational power
torque X angular displacement/time
also torque X angular velocity
T x AD or T x AV
Strength to mass ratio
strength divided by mass - S/M
remember: F=M x A, this means A=F/M. As athlete acquires more muscle mass, athlete can produce more greater force, however this is not perfect. Increase in force that accompany increases in mass are generally less than the increases in mass. Thus, athlete is stronger but slower.
Agonist
That which causes motion.
May be muscle, gravity, or some outside influence such as wind.
When the primary mover is not muscle, then the agonist should be viewed as a mechanical agonist
Antagonist
that which opposes/resists motion
May be muscle, gravity, or outside influence such as water.
When the primary resistance is not muscle, then the antagonist should be viewed as a mechanical antagonist
mechanical agonist
primary mover is not muscle, like wind
mechanical antagonist
primary resistance is not muscle, like water
that which causes motion, may be muscle, gravity, outside forces like wind
agonist
that which opposes/resists motion, may be a muscle or gravity or some outside influence like water
antagonist
Synergists
when muscles cooperate to produce motion which neither could create by itself.
What are the subcategories of synergists?
Assistors, Stabilizers, Neutralizers
assistors
muscles which work in concert with primary agonist (primary mover) to produce the desired movement; secondary and tertiary agonists
stabilizers
muscles act to stabilize a body part so that a desired motion can be produced.
Give example of a stabilizing exercise
1.seated rows erector spinae stabilize back trapezius & rhomboids stabilize the scapulae 2.push ups abdominal stabilize torso
neutralizers
special stabilizers - muscles counteracts the undesired effect of a biarticular muscle.
Give example of a neutralizing stabilizing exercise
ascending in squat
rectus femoris, biarticular muscle, causes both extension at knee and flexion of hip.
extension of knee desirable, but flexion of hip not desirable. The gluteal group acts to cancel flexion
Projectile
an object/body that has been propelled into the air and then allowed to free fall. Once airborne only air resistance and gravity will affect its flight.
What is the horizontal displacement of a projectile called?
Range
What are 3 factors that influence range?
1) velocity of projectile at its release point
2) angle of release
3)relative projection height (comparison of height of release and height of landing point)
the projecting of objects is almost always initiated by a ballistic type of force.
Tangential Velocity Formula
Often, we with t relate the rotational velocity of an object to its ultimate linear velocity.
The tangential velocity of an object is calculated by multiplying its angular velocity by the radius of the circle in which it is rotating
AV x R= tangential velocity
Vector
a quantity that reflects both magnitude and direction.
Vector => velocity and weight
Scalar
quantity only reflects magnitude.
Scalar => speed and mass
Vector Resolution
single vector being broken down (resolved) into its vertical and horizontal components
I_ graph
Resultant vector
name/result of vector when combining two or more vectors
Vector Composition
act of combining two or more vectors
Vector Analysis
term used to describe the vector resolution and vector composition
Vectors are often represented as _____ with the length of the arrow representing the _____ and the arrowhead indicating the _____. If the arrow represents force, then the force is applied at the _____. Vectors have both a _____ and _____ components.
arrows magnitude direction tail vertical horizontal
