FA&K chapter 8 Flashcards
Kinesiology
Study of how the body moves
Mechanics
Study of forces
Biomechanics-
Applying mechanics to the human body
Static
Non-moving systems
Dynamics
Moving systems
Kinetics
Forces causing movement in a system
Torque
The tendency of force to produce rotation around an axis
Friction
A force developed by two surfaces Tends to prevent motion of one surface over another
Kinematics
Involves: -Time -Space -Mass
Osteokinematics
Manner in which bones move( w/o regard to the movement of joint surfaces)
Arthrokinematics
The manner in which adjoining surfaces move in the relation to each other
Force
-a push or pull -Represented as a vector (->)
Vector
A quantity having both magnitude and direction
Velocity
vector that describes speed (measured in units)
Scalar
A quantity that describes only magnitude -Length -Axes- -Volume -Mass
Inertia
Property of matter that causes it to resist any change of its motion in either speed of direction (mass is measured of inertia)
The Law of Inertia
An object @ rest stays at rest, and an object in motion tends to stay in motion
The Law of Acceleration
The amount of acceleration depends on the strength of the force applied to the object
The Law of Action-Reaction
Foe every action, there is an equal and opposite reaction
Mass
The amount of matter in an object
Two types of force
-Internal -External
Internal Force
-Muscle Contraction -Ligament Restraint -Bony support
External force
-Gravity -Externally applied resistance
Characteristics of force
-magnitude -direction -point of application
Linear Force
Results when 2 or more forces are acting along the same line (tug of war)
Parallel Force
Occur in the same plane and in the same or opposite direction ( 3 point pressure system)
Concurrent Force
2 or more fores must act on a common point but must pull or push in different directions
Force couple
Occurs when 2 or more forces act in different directions, resulting in a turning effect
Movement of force/rotary force
The ability of force to produce rotation around an axis
How much torque can be produced depends on?
-Strength of the force -Torque arm -torque is the > when the angle of pull is 90* -Torque < as the angle of pull decreases or the increase from the perpendicular position
Stabilizing force
A force generated by the muscle that is directed back into the joint pulling 2 bones together
Angular Force
The greater the angular force a muscle can produce the more movement will occur at the joint ( greatest at 90*)
Dislocating Force
Passed 90* the stabilizing force becomes a dislocating force because the force is directed away from the joint
The state of equilibrium
All torques acting on an object are even and the object is balanced
Gravity
The attraction between earth and an object
COG
The balance point of an object at which the torque on all sides is = (Located slightly anterior to S2)
BOS
The part of the body that is in contact w/ the supporting surface
LOG
An imaginary line passing through the COG toward the center of earth
Stable Equilibrium
An object is in a position where disturbing it would require the COG to be raised
Unstable Equilibrium
Occurs when only a slight force is needed to disturb and object
Neutral
Exists when an objects COG is neither raised or lowered when it is disturbed
The lower the COG……
The more stable the object
The COG and LOG must remain w/in the….
BOS for an object to remain stable
Stability increases,,,,
As the BOS is widened in the direction of the force
The greater the mass of an object…
The greater its stability
The greater the friction between the supporting surface and the BOS….
The more stable the body will be
Lever
Rigid, can rotate around a fixed point when a forces is applied ( BONE)
Axis (Fulcrum)
A fixed point around which the lever rotates (JOINT)
Force
Effort- causes the lever to move (MUSCLE)
Resistance
Load-Must overcome the motion to occur -weight of the part being moved -pull of gravity on the part -external weight being moved by the body
Force Arm
The distance between the force and the axis
Resistance Arm
The distance between the resistance and the axis
Longer FA=
Easier to move the part
Longer RA=
Harder to move the part
First class lever (def.)
The axis is between the force and resistance
First class lever: Axis close to resistance= Short RA/Long FA
-Easy to move the resistance -Resistance is moved only a short distance -Force has to be applied through a long distance -By placing the axis close to the resistance, you have a lever that favors force
First class lever: Axis close to force= Short FA/Long RA
-It is harder to move the resistance -Resistance moves a longer distance -Force is applied through a short distance -By placing the axis close to the force, you have a lever that favors distance(ROM) & speed
Second Class Lever (wheel barrow)
The resistance is in the middle w/ the axis at one and the force at the other end
Second Class Lever: Long FA/ Short RA
The longer the FA, the easier it is to move the part
Second Class Lever:Long RA/ Short FA
The longer the RA, the harder it is to move the part
Third Class Lever
Force is in the middle w/ the resistance & the axis at the opposite ends
Third Class Lever: Short FA
The load is harder to move, but moves a greater distance
Third Class Lever:Long FA
The load is easier to move, but doesn’t move as far -Any gain in distance is lost in power - The advantage of a third class lever is speed and distance (MOST COMMON LEVER IN THE BODY)
Pulley Purpose
To either change the direction of a force or to increase/decrease its magnitude
Fixed Pulley
-Simple pulley attached to a beam -acts as a first-class lever w/ the force on one side of the pulley(axis) and the resistance on the other -Used only to change direction
Moveable Pulley
-1 end of the rope attached to a beam, the rope runs through the pulley to the other end where the force is applied -The load (resistance) is suspended from the moveable pulley -The purpose of this type of pulley is to increase the mechanical advantage of the force
Mechanical Advantage
The # of times a machine multiplies the force
Wheel and Axle
-A lever in disguise -Consists of a wheel/crank attached to & turning together w/ and axle -Used to increase the force exerted -the larger the wheel in relation to the axle, the easier it is to turn the object -Application? (Patient w/ arthritis unable to turn on/off faucet)
Inclined Plane
-A flat surface that slants -Exchanges increased distance for less effort Application? Wheel chair ramp
