 | Term | Definition |
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Speed |
displacement per unit time (ft/sec or m/s) |
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Velocity |
(v) displacement per unit time in a specific direction (speed limit) |
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Linear velocity |
measured in ft/sec |
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Angular velocity |
measured in degrees/sec |
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Acceleration |
(a) (increase speed) the change in velocity per unit time (ft/sec^2 or m/s^2) |
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Mass |
(m) amount of matter contained in an object, measured in slugs or kilograms (kg): Mass remains constant, but weight changes |
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Force |
(F) =(m)(a) a push or pull applied to an object or person, measured in pounds (lbs) or Newtons (N): When meas. weight, we measure force |
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Weight |
(m)(g) (gravity=9.8 m/s^2 or 32.2 ft/sec^2) the force due to gravity exerted on a mass |
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Vectors |
arrows drawn on a force diagram to represent location of the force, magnitude of the force, and direction of the force |
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Normal Force |
(N) the force perpendicular to a surface that prevents an object from falling through the surface. |
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Compression |
a smashing force created by at least two pushes |
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Tension (tensile force)/ Traction |
created by forces pulling in opposite directions |
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Distraction |
separation of tissues in the body created by tensile forces |
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Torsion |
a twistingforce, like wringing-out a washcloth |
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Shearing |
created by two opposing forces that are not in line with each other |
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Torque |
(T)= (F)(MA) (moment arm) a force that creates rotational movement; the muscles in the body create torque in order to flex or extend joints |
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Moment arm |
(MA) the perpendicular distance from the center of motion to the line of force |
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Friction |
a force that is parallel to a surface and resists movement |
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Free body diagram |
drawings that show the forces placed on objects or people |
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Center of mass/gravity |
(COM)/(COG) IN THE ANATOMICAL POSITION: is located just anterior to S2 (the 2nd sacral vertebra) |
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Lever |
A rigid segment (the bones are assumed to be rigid, while in reality they are not) |
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Fulcrum |
A component of a lever system; the COM and location of the axis of motion; the joint |
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Force |
A component of a lever sys.; the pull of a muscle |
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Resistance |
the weight being moved (can be a body part) |
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Mechanical advantage |
the ease with which the resistance can be moved; moving the resistance |
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Longer lever arm of the force |
less force is needed to move the resistance |
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Longer lever arm of the resistance |
more force is needed to move the resistance |
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First class levers |
the fulcrum is located btwn the force and the resistance |
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Second class levers |
the force and the resistance are on the same side of the fulcrum; the resistance is closer to the fulcrum |
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Third class levers |
the force and the resistance are on the same side of the fulcrum; the force is closer to the fulcrum |
