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Definition
-The branch of physics which examines the effect of forces on an object and the motion those forces create
- all motion, human or not is the product of the application of force and is subject to the laws and principles that govern force and motion
-has two arenas: static and dynamic
-has two arenas: static and dynamic |
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-The aspect of science which examines the basic laws governing the effect forces have on the state of rest or motion of any living system
-The application of mechanical principles to living beings |
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-Refers to situations in which forces acting on a body are balanced and the body is in equilibrium
-a body in ____ equilibrium would exhibit either no motion or a constant motion which does not result in a change in position
-key in understanding and identifying centers of gravity and buoyancy |
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Definition
-covers circumstances in which forces acting on a body are unbalanced
-the principles behind this explains how an excess of force can cause a body to change in direct or speed or motion
-principles of work, energy and acceleration are key |
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| Forces that modify motion |
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Definition
1. weight
2. Contact Forces
3. Fluid Forces |
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| the amount of force generated by gravitational pull on an objects COG, relative to the object's mass, and directed toward the earth's center |
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the "reaction" force applied by the earth's surface in response to force applied to it by a body
- without this there would be no motion |
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the force that resists efforts to roll or slide one object's surface against another
-without this it would be impossible to conduct controlled motion! |
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upward force applied by a liquid which counters the force of weight of an object place in the liquid
-objects in water weigh less due to this acting on them |
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| what does buoyancy count? |
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Definition
| Ground Reaction is countered by... |
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| objects in water weight less due to what forces acting on them? |
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Definition
Buoyancy
-what does this force do when an object is in water? |
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Definition
-the fluid resistance to movement by an object through water or air
-resistance to forward motion
-is the product of pressure on the object's boundary (surface ___) and backward pull by turbulence (form ___)
-swimmers shave to reduce surface ___ |
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-friction along the object's boundary
-swimmers shave to reduce this |
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-backward pull by turbulence behind
-streamlining reduces this |
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-the results of changes in fluid pressure as the result of differences in airflow velocities
-fluid pressure decreases as speed increases
-aircraft wings operate on this principle; the top curvature of a wing is greater than the bottom, it will have lower pressure then the bottom creating ___ |
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buoyancy, drag, lift
are all... |
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| Ground reaction force and friction are what kind of forces? |
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Definition
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| Linear forces (composite) |
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Definition
| all forces occur along the same line of action |
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| Concurrent force (composite) |
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Definition
| forces acting at different angles are applied at the same point |
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| parallel forces (composite) |
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Definition
| forces not in the same action line but parallel to each other acting at different points on a body |
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| linear, concurrent, parallel |
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Definition
increase the rotary component such as with the quadriceps at the knee
-change the direction of a muscle's line of pull such as peroneus longus at the lateral malleolus
-act to move one segment or lever relative to another as pronator teres rotaes the radius over the ulna
-ligaments and tendons can act as this too |
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Definition
-seeks to change the direction of force by changing the angle of pull
-where it not for these , some muscles would be unable to move whatsoever |
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Definition
objects start moving when they are pushed or pulled, when this is acts on them
-this produces, prevents, and stops motion; increase or decrease speed or change an objects direction of travel
-they are the effects one body has on another |
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Definition
-those forces exerted on bodies by other bodies within a defined system
-cause change in body shape
-ex. muscles |
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-forces exerted by bodies within an arbitrarily specified system on bodies outside the system
-cause displacement of the body
-ex. gravitation force, friction, wind/water resistance |
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Definition
1. Magnitude
2. Direction
3. Point of application |
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-amount of size of force being applied
-___ of muscular force is directly proportional to the number and size of the fibers in the muscle that is contracting |
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| When does mechanical axis of bone not run lengthwise through shaft? |
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Definition
bones that have bend (ribs)
articular facets
femur |
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Definition
| the turning effect of eccentric force |
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| Torque (combination of what 2 things) |
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| Force magnitude x length of force arm |
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| When movement on an object is observed, what two inferences may be made? |
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Definition
1. A force was applied to the object to set it in motion
2. the force was great enough to overcome inertia |
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Definition
-motion in a straight line progression
-the object, the sum of all its parts are moving in the same direction and at a uniform rate of speed |
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Definition
-motion of an object along a curved path
-includes circular motion; that is, the movement of an object along the circumference of a circle, maintaining a constant radius |
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| most joints are ____ and undergo primarily ____ motion |
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| Deals in terms of displacement, velocity, and acceleration and disregards forces which cause or modify the motion |
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-distance an object is removed from its starting point
-a vector quantity with magnitude and direction |
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Definition
-vector quantity related to displacement. it is speed in a given direction
= displacement/time |
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Definition
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-when rate of displacement does not change
- when distance and direction remain the same for each equal period of time
-velocity is constant |
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| acceleration can occur under two conditions |
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Definition
1. Change in speed
2. Change in direction |
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Term
Angular kinematics
-what does it account for?
-how different from translatory |
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Definition
accounts for displacement, velocity, and acceleration
-diff from trans: rotary movement involved
- units used to describe quantities are different |
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Definition
-product of angular motion
-movement of a rigid lever about an axis (like many of the human joints)
=1 revolution=360 degrees=2pie |
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Definition
rate of rotary displacement
-equal to the angle through which the lever turns divided by the time it takes for the displacement (degree/sec)
-may be uniform or non-uniform
-most movement by humans of this are non-uniform |
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| Relationship btwn angular velocity, lever length and linear velocity (baseball) |
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Definition
Greater force is imparted to a struck object when the radius of the striking implement is longer because the greater linear velocity is generated at its end
- there exists a proportionality in that to achieve higher linear velocities, motions must be done with longer levers or higher angular velocities |
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Definition
| -the point at which all forces acting on the body are zero |
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| object's shape or position |
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| in quiet standing, COG is where |
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Definition
| directly over the center of pressure |
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Definition
| The point at which the force vector of GRF is applied |
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Definition
-the movement in region of the head which produce pendulum-like motion in COG
-pendulum-like motion changes the center of pressure |
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Definition
occurs when an object is in a position in which the COG must be raised by the effort to disturb it
-the more COG needed to raise it, the more stable it is |
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Definition
| Exists in a circumstance in which very little effort is required to disturb the object |
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Definition
| Circumstance in which the COG does not need to move to destabilize the object such as a ball |
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| Most critical factors affecting Stability (3) |
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Definition
1. Size and shape of base of support
2. Height of COG
3. Relation to line of gravity's pull to the base of support |
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Definition
| The part of the body in contact with the supporting surface as well as the intervening area |
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| Lower COG, the more stable because it allows greater ____ _____ within the bounds of the base of support |
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Definition
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| Lower COG, the more stable because it allows greater ____ _____ within the bounds of the base of support |
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Definition
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| Positions of instability occur when |
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Definition
| gravity changes from a linear to a rotational force or torque |
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Term
| How do we compensate when carry heavy object at arms length or walk on beam? |
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Definition
We lean or counterbalance by changing COG
We create counter force |
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| Visual and Psychological factors of stability |
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Definition
| labyrinth of inner ear has fluid in it which lets us know what our head is doing. also from eyes, ect. |
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Dynamic
-how its related to posture |
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| Postural stability measured by.. |
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Definition
| = motion of COG and center of pressure |
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Term
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Definition
| Occurs when individuals stand on a slop, stand on a moving surface, stand on one foot or carry a weight against the front of the body |
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| Adjustments for postural sway are automatically made via... and ... |
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Definition
| proprioceptors and feedback mechanism |
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Term
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Definition
-ability of a body or an object to displace by means of it's own mechanisms or power
- in humans it is the lever systems of the body which create propulsion
-if this occurs in any human, there must be a resistance against which a body segment, acting as a lever, can push to generate a reaction force |
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Term
| Walking is the combination of (3 things) |
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Definition
= muscular activity + nervous system function + synchronized joint movement
= this creates fluid movement with perfect detail |
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| Periods of the Support Phase |
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Definition
Heel Strike, Foot-flat, Midstance, Heel-off, Toe-off
- toe-off period of one foot overlaps with heal and foot-flat of other foot creating double support |
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Term
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Definition
| One full lower extremity cycle; the heel strike on one foot to the next heel strike on the same foot |
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Definition
| The heel strike of one foot to the heel strike of the opposite foot |
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Definition
| In this phase, gravity and momentum represent the chief sources of motion creating ballistic motion |
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Definition
-In this phase, first half is produced by the momentum of the forward moving trunk
- 2nd half by contraction of the extensor muscles of supporting leg |
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Term
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Definition
| Load heel with breaking force (decelerate) and prepare for weight baring forces |
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| Know phases and order of gait! |
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Definition
| Initial contact, loading response, midstance, terminal stance, pre-swing, initial swing, mid-swing, terminal swing, initial contact |
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Term
Propulsive force (push up and forward)
overcomes.... |
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Definition
Inertia of the body
is overcome by... |
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Term
| The great the weight of body |
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Definition
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| Restraining Force in mechanical analysis |
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Definition
| What the foot in the swing phase provides to the forward motion of the trunk |
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Term
GRF counters in mechanical analysis
-use GRF to move, decelerate or stop movement |
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Definition
The force of the body's falling weight in mechanical analysis
countered by... |
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Definition
| Creates a braking effect against the downward pull of gravity and the forward motion of inertia |
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Definition
| Creates a propulsion effect by combining the force of musculoskeletal leverage with GRF |
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Definition
| Dependent upon the correct balance of pressure of the foot and counter-pressure of the supporting surface |
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| Friction (in mechanical analysis) |
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Definition
-counters the horizontal component of force
-allows for the transmission of the GRF
-the greater the horizontal component of force such as walking with a long stride, the greater dependence up on this |
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Definition
-good ____ of the lower extremities reduces friction in the joints and decreases the likelihood of strain and injury
-the stability of the weight-bearing limbs and the balance of the trunk over these limbs are important factors in efficiency of gate |
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Definition
| -Unnecessary lateral movements, usually the product of excessive motion in the pelvic or should girdles, decrease gait economy |
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Definition
-Sufficiently long and pliable muscles, ligaments and fascia reduce internal resistance and thus, the amount of force necessary for walking
- Elasticity and extensibility, particularly in the diarthrodial muscles of the lower extremities add to gait efficiency |
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Definition
-Properly functioning relfex arcs contribute to a well-coordinated and efficient gait
-injury, disease and chemical substances interfere with the walking reflex |
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