Ch. 11: Levers and Torque

Question 1

3 characteristics of force

Answer 1

-magnitude
-point of application (center of attachment of the muscle to the bony lever)
-direction (parallel to mm fibers)

Question 2

another word for stabilizing

Answer 2

compressing

Question 3

another word for destabilizing

Answer 3

distracting

Question 4

whether a force is stabilizing or destabilizing depends on what

Answer 4

the angle of mm pull at that jt

Question 5

the angle of mm pull at a jt is b/w the mm and bony lever and is taken _____ to the _____

Answer 5

closest, jt

Question 6

another word for vertical component

Answer 6

rotary component

Question 7

the rotary component is always _______ to the bony lever

Answer 7

perpendicular

Question 8

when does the horizontal component stabilize and destabilize the jt

Answer 8

stabilize: at JT angles less than 90 degrees
destabilize: at JT angles greater than 90 degrees

Question 9

anatomical pulleys act to change the _______ of _____

Answer 9

direction, force

Question 10

increasing the angle of pull _______ the rotary component and _______ efficiency of action

Answer 10

increases, improves

Question 11

a rigid bar (bone) that can rotate around a fixed point when a force is applied

Answer 11

lever

Question 12

the portion of the rigid bar b/w the fulcrum/axis and the force point; may be an effort arm or resistance arm

Answer 12

lever arm

Question 13

3 classes of levers w/ example for each

Answer 13

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

Question 14

3 considerations in determining class of a lever

Answer 14

1. point at which effort force is applied
2. point at which resistance force is applied
3. point at which fulcrum is located

Question 15

where does the axis lie in a first class lever and whats the advantage

Answer 15

axis lies b/w the effort and resistance and the advantage is balance

Question 16

advantage and disadvantage of second class levers and where does the resistance lie in relation to the fulcrum and effort force

Answer 16

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

Question 17

where does the effort force lie in a third class lever and what’re the advantages and disadvantages

Answer 17

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

Question 18

the turning or rotating force

Answer 18

torque

Question 19

do the vertical component and horizontal component of mm force vector contribute to torque

Answer 19

only the vertical component

Question 20

when is mm torque the greatest

Answer 20

when the mm force vector is applied at 90 degrees to its bony lever

Question 21

when is a moment arm the longest

Answer 21

when the force vector is entirely composed of a vertical component (meaning the force vector is applied 90 degrees to its bony lever)