PowerPoint 3 Flashcards
What are the two general approaches to qualitative analysis?
Composite approach
Component approach
What is the composite approach?
Also known as the total body approach, views the whole body as a system that progresses through phases as it refines movement patterns
Total body approach often referred to as “developmental biomechanics”
Breaks down movement patterns into primary body parts
However, the stages of skill progression are based on the product of all body parts in combination.
Each stage identifies important body parts used to perform the skill, and the number of stages can vary depending on the requirements necessary to perform a task.
What is the component approach?
Uses the same phase/stage method (defined as steps), but rather than looking at the body as a global system, it breaks the body down into component sections
Sometimes called “error analysis strategy”
Each primary body component is observed.
Ex: Foot Action, Trunk Action, Backswing, Humerus action, Forearm.
Each component has its own evaluative series of stages or phases that can be advanced independently of each other.
Performers could show evidence of mature skill performance in one part of the body, while other body segments are at less mature levels.
Where does quantitative motion analysis stem from? (examples)
Stems from the simple need for a deeper and more specific understanding of why the system moves the way that it does
(Enhance performance of elite athletes
Physical therapists and athletic trainers have a need to quantify severity of injury and/or treatment success.
Biomechanical research—goal of understanding human motion, optimizing sport performance, improving equipment design, and/or preventing injury)
Scalar quantity?
A quantity that possesses only a magnitude but has no particular associated direction
Mass?
Quantity of matter of which a body is composed; a measure of a body’s inertia
Inertia?
A body’s resistance to having a state of motion changed by the application of a force
Vector quantity?
Can only be fully specified with a magnitude of appropriate units and a precise direction
Weight?
A measure of the force with which gravity pulls upon an object’s mass
What are arrows used for in free-body diagrams?
Arrows are used to represent forces in free-body diagrams.
Arrows are appropriate because all forces are vectors.
What principles should be kept in mind when drawing vectors?
A tip and tail, a length drawn to scale, and an imaginary path along which it would travel
What are the five areas of graphical representation of force and the definitions of these areas?
-Direction: the way in which the force is applied
-Orientation: alignment or inclination of the vector in relation to cardinal directions
-Point of application: the point or location at which the system receives the applied force
-Magnitude: amount or size of the applied force
-Line of action: imaginary line extending infinitely along the vector through the tip and tail
What does biomechanics require a description of?
Single points, segments, and forces
____ ____ ____ allows for specific definition of an objects position in space by establishing one or more frames of reference?
Cartesian coordinate system
It is sometimes more convenient and necessary to define a ____ ____ ____ and locate a point in space using its ____ ____ ____?
Polar coordinate system… plane polar coordinates
SOHCAHTOA
Sin=opposite/hypotenuse
Cos=adjacent/hypotenuse
Tan=opposite/adjacent
Pythagorean theorem?
R^2 = X^2 + Y^2
What is trigonometry based on?
Simple ratios of the lengths of two sides in a given triangle
What is vector equality?
Two vectors are considered equal if they possess the same magnitude and direction (A = B)
Commutative law of addition?
When vectors are added together, the sum is independent of the order of addition (A + B = B + A)
Associative law of addition?
The sum of three or more vectors is independent of the grouping of the vectors for addition. (A + B) + C = A + (B + C)
What is vector subtraction?
Negative of a vector: a vector that when added to the first gives a sum equal to zero (the vectors that have the same magnitude but point in opposite directions). A + (-A) = OA – B = A + (-B)
What is vector multiplication?
When multiplying (or dividing) a scalar by a vector, the product is a vector quantity, e.g., scalar number = -9, vector = A. The product of scalar x vector = -9A
Multiplying one vector by another results in another vector: A x B x C
How can graphical vector analysis be used?
Can be used to understand:
the multiple effects of one force
the resultant motion of the system that is acted upon by many different forces simultaneously
What is vector resolution?
Process by which individual directional component vectors of a single vector are determined
What are component vectors?
The individual vectors that represent each of the multiple effects that one vector represents
What is a vector resolved into?
Horizontal component (parallel to the x-axis)
Vertical component (perpendicular to the x-axis)
What is vector composition?
Two or more vectors are summed to determine a single resultant vector, i.e., a situation where multiple forces act upon a system, and we would like to find the resultant force vector
What is a resultant vector?
-A vector that represents the sum of all forces acting upon a system
-Resultant motion of a system that we observe is composed of many individual forces
-Forces may be applied simultaneously or sequentially.
What are two factors that affect the complexity of vector composition?
Number of vectors
Relative directions and orientations of the vectors
Muscle groups produce force along ____ lines which converge in one ____ ____ ____?
Multiple… one resultant line
A single muscle force can have ____ ____ effects?
Multiple directional
Describe Q angle, the differences between male and females, and the implications?
Differences in Q angle related to gender
-Q angle (quadriceps angle) is a rough estimate of femoral and tibial alignment.
-Females generally have a larger Q angle due to wider hips (muscle insertion sites).
-Larger Q angle deviation is correlated with patellofemoral pain.
Force?
Something with the capability to cause a change in motion of a system
A “pull” or “push”
Force Changes Motion - Does not cause change in motion
Motion can exist without force
Doesn’t have to change motion but it could.
Force also can cause change in the shape of a system.
What are the five properties of force and the definition of these properties?
Direction: the way in which the force is applied
Orientation: alignment or inclination of the vector in relation to cardinal directions
Point of application: point or location at which the system receives the applied force
Magnitude: the amount or size of the applied force
Line of action: an imaginary line extending infinitely along the vector through the tip and tail
What is Newton’s 1st law?
Law of Inertia
A system at rest will remain at rest. A system in motion will remain in motion(straight line) unless acted upon by an external force.
Natural tendency of a system is to resist change in motion
Does not mean no motion, Rather no CHANGE in motion without Force.
What is inertia?
Inertia – Resistance of a system to having a state of motion
Proportional to mass
No units used to represent inertia
What is mass?
Mass(m) – a measure of a systems inertia.
Quantity of matter composition a body
Kg
The greater the mass of an object, the greater the tendency to stay in the current state of motion.
What is Newton’s second law?
Law of Acceleration
The acceleration of a system is directly proportional to the sum of the forces (net forces) acting upon it and inversely proportional to its mass.
Change in motion is directly proportional to the magnitude of the applied force.
The observed change in motion is an acceleration.
What is Newton’s thrid law?
Law of Action–Reaction
To every action there is always opposed and equal reaction, or the mutual actions of two bodies upon each other are always equal and directed to contrary parts.
Forces exist in pairs (i.e., one force acts on two objects).
Often misinterpreted:
Every action force is met with an equal and opposite reaction force, but every action does not produce an equal and opposite reaction; see Law Two.
What is the law of universal gravitation: the law of attraction?
Every body in the universe attracts every other body with a force directed along the line of centers for the two objects that is directly proportional to the product of their masses and inversely proportional to the square of the separation between the two objects.
Attempts to explain the interaction of objects, even when they are not in contact.
The greater the mass, the greater the forces of attraction
The closer the bodies, the greater the forces of attraction.
What is a field/field-force?
Field: any object possessing mass creates an invisible field of influence stretching throughout space, allowing it to act on an object without making physical contact. Field-Force is a non-contact force.
Two magnets held in close enough proximity; The moon orbiting the earth
What are the 4 types of field forces?
-Strong nuclear forces
-Electromagnetic forces
-Weak nuclear forces
-Gravitational forces
What type types of force are biomechanics concerned with?
Electromagnetic and gravitational forces
Strong nuclear force?
Occurs between subatomic particles which prevents the nucleus of an atom from exploding because of the repulsive electric force produced by its protons
Electromagnetic force?
Between electric charges
Weak nuclear force?
A product of some radioactive decay process
Gravitational force?
Exists between bodies of mass
What are contact forces?
Exists between bodies of mass
What are external forces?
-Those that interact with the system from the outside (extrinsic)
-The external movement environment
-Only external forces can change the motion of the system.
What are internal forces?
-Act within the defined system (intrinsic)
-Internal to the system
-Only internal forces can change the shape of the system.
What is an action force?
“The force,” the initially applied force
What is a reaction force?
The simultaneous equal counterforce acting in the opposite direction to the action force
Describe gravity?
Actually relatively weak force.
Egg Drop from a 5 story building
Jumping
However, one of the most pervasive external forces in the everyday life of the human system.
Gravitational pull is concentrated at the center of mass.
Gravity pulls on an object’s mass with a certain amount of force.
Describe weight?
Measure of the force with which gravity pulls upon an object’s mass;
weight (as opposed to mass) is a vector because it has a direction
Weight changes as we get closer to and farther from the center of the Earth’s mass.
Did you know?? A person will weigh slightly less at the equator (further from the center of the Earth) and slightly more at the poles (closer to the center of the Earth’s mass).
Weight = ____ x ____?
Mass x acceleration
What is friction?
Force that resists the sliding of 2 objects in contact
Exists whenever two objects are in contact and have the potential to slide across each other.
Friction force vectors have an opposite direction of the potential sliding direction and parallel to the two surfaces in contact.
What is normal force?
Force that acts downward on one surface and upward on another; presses the two surfaces together
Responsible for the system’s center of gravity being temporarily elevated during locomotion.
System applies normal force to the ground that is met with an equal and opposite normal force from the Earth, elevating the system’s center of gravity.
Ground reaction force: the oppositely directed normal force of the ground
Every contact between foot and ground creates an upward reaction force
Fatigue does not impact GRF
What are the two kinds of friction?
-Static (keeps an object from moving)
-Kinetic (Opposes the sliding motion of an object)
How are the coefficients of friction shown and which one is greater?
Coefficient of static friction (μs)
Coefficient of kinetic friction (μk)
Static friction > Coefficient than Kinetic friction
What is rolling friction?
Rolling friction: exists whenever one surface is rolling over another but not sliding
Just like static and kinetic friction, rolling friction depends on a coefficient of friction and normal force.
The coefficient of rolling friction is less than both static and kinetic friction.
One molecular surface is being “peeled away” from another, so imperfections are not “bumping” into each other.
Examples
Care tires
Paint Roller
Anti-lock breaks
What is pressure?
Pressure: the magnitude of applied force acting over a given area
Famous magic trick is a person lying on a bed of nails. Its not magic, its science! Magician is manipulating pressure to avoid being punctured by the nails:
Weight of magician = applied force (F)
Area over which it is applied = the total area of the tips of the nails (A).
𝑃= 𝐹/𝐴
We use pressure in medicine all the time.
Measuring the pressure of our Eyes, Blood vessels.
In the musculoskeletal system, externally applied forces are often “____.”
Pulls
What is stress?
Stress (sigma): the external force acting to deform the material
Similar to pressure, in that it is calculated as an external force (F) acting over a given cross-sectional area (A):
“sigma” =F/A
What is strain?
Strain: the resulting magnitude of deformation as a result of the applied stress
The percentage change in length due to an applied stress
ε = strain
delata l = change in length (lfinal - linitial)
li = initial or original length
ε =(𝑙𝑓−𝑙𝑖)/𝑙𝑖
What is Hooke’s Law?
Strain is proportional to stress in accordance with Hooke’s Law.
That relationship is a constant for a given material and particular type of deformation
What is an Elastic modulus?
relationship of stress (sigma) and strain (ε) for a given material and type of deformation:
E = “sigma” /”ε”
What is the five elastic modulus?
Tension stress: occurs when two forces are applied to a system in opposite directions away from each other. “Pulling apart”
Compression stress: the result of two forces being applied to the system in opposite directions toward each other
Shear stress: occurs due to application to two parallel forces that tend to simultaneously displace one part of a system in a direction opposite another part of the system
Bending: occurs when two off-axis forces are applied such that tension stress is caused on one side of the system and compression stress occurs on the other side
Torsion: caused by two forces being applied in such a way that part of the system is rotated around its longitudinal axis in a direction opposite rotation of another part of the system
Stress/strain curves of all materials are not ____?
Linear
Elastic region?
The linear portion of any given stress/strain curve
The material will return to its original shape if the tensile stress is removed within this range.
What is the yield point?
Point at which the applied stress can lead to permanent deformation
what is the plastic region?
Non-linear response of the material after the yield point
Some degree of deformation will persist after the removal of the stress.
Materials vary in their ability to reform after ____?
Deformation
What is the coefficient of resitution?
(or coefficient of elasticity) is a parameter observed after reformation that indicates the ability of an object to return to its original shape after deformation
The higher the coefficient of restitution, the greater the energy remaining after impact
A common application in sports is to calculate a coefficient of restitution (e) for a particular type of ball by dropping the ball from a known height and observing the rebound.
e = √”hrebound” ∕”hdrop”
Theoretically ranges in value from 0.00 to 1.00
0.00 being perfectly inelastic
1.00 being perfectly elastic
Viscoelastic?
A material whose deformation is affected by both the rate of loading and the length of time that it is subjected to a constant load
Most biological materials are viscoelastic to some degree because of their fluid components.
Creep?
Property of experiencing increasing strain (continued deformation) under a constant stress
Stress relaxation?
The corresponding eventual decrease in stress that will occur as fluid is no longer exuded
