Ch. 11: Levers and Torque Flashcards
3 characteristics of force
-magnitude
-point of application (center of attachment of the muscle to the bony lever)
-direction (parallel to mm fibers)
another word for stabilizing
compressing
another word for destabilizing
distracting
whether a force is stabilizing or destabilizing depends on what
the angle of mm pull at that jt
the angle of mm pull at a jt is b/w the mm and bony lever and is taken _____ to the _____
closest, jt
another word for vertical component
rotary component
the rotary component is always _______ to the bony lever
perpendicular
when does the horizontal component stabilize and destabilize the jt
stabilize: at JT angles less than 90 degrees
destabilize: at JT angles greater than 90 degrees
anatomical pulleys act to change the _______ of _____
direction, force
increasing the angle of pull _______ the rotary component and _______ efficiency of action
increases, improves
a rigid bar (bone) that can rotate around a fixed point when a force is applied
lever
the portion of the rigid bar b/w the fulcrum/axis and the force point; may be an effort arm or resistance arm
lever arm
3 classes of levers w/ example for each
First class: ie) your head tipping back
Second class: ie) calf mms pulling on the calcaneal tendon to stand on toes
Third class: biceps flexing forearm
3 considerations in determining class of a lever
- point at which effort force is applied
- point at which resistance force is applied
- point at which fulcrum is located
where does the axis lie in a first class lever and whats the advantage
axis lies b/w the effort and resistance and the advantage is balance
advantage and disadvantage of second class levers and where does the resistance lie in relation to the fulcrum and effort force
Advantage: magnifies the effect of the effort therefore it takes less force to move object
Disadvantage: requires lots of effort to move through a larger ROM
Resistance lies between the fulcrum and effort force
where does the effort force lie in a third class lever and what’re the advantages and disadvantages
effort force lies b/w the fulcrum and resistance force.
Advantage: increased ROM at the resistance end from small ROM at the effort end
Disadvantage: increased effort needed to overcome the resistance
the turning or rotating force
torque
do the vertical component and horizontal component of mm force vector contribute to torque
only the vertical component
when is mm torque the greatest
when the mm force vector is applied at 90 degrees to its bony lever
when is a moment arm the longest
when the force vector is entirely composed of a vertical component (meaning the force vector is applied 90 degrees to its bony lever)
