LECTURE #14 - torques and moments of force

Question 1

what are the 4 factors of force in regards to torque ?

Answer 1

• magnitude
• point of application
• direction
• line of action

Question 2

what is a moment arm ?

Answer 2

perpendicular distance between line of action of force and axis of rotation

Question 3

what are levers ?

Answer 3

simple machine consisting of a relatively rigid bar that may rotate about a fulcrum

Question 4

between the bone and joint, which is the rigid bar and which is the fulcrum ?

Answer 4

bone = rigid bar
joint = fulcrum

Question 5

when force is applied to a lever what does it move ?

Answer 5

a resistance

Question 6

what are the 3 components of levers ?

Answer 6

• axis of rotation (fulcrum)
• motive forces (from our muscles)
• resistive forces (from weight of limbs or objects)

Question 7

describe the 1st component of levers : axis of rotation (fulcrum) :

Answer 7

lever rotates around this axis

Question 8

describe the 2nd component of levers : motive forces (from our muscles) :

Answer 8

cause rotations

Question 9

describe the 3rd component of levers : resistive forces (from weight of limbs or objects) :

Answer 9

resists rotation

Question 10

what are the three arrangements of rotation for a lever ?

Answer 10

force, resistance and axis

Question 11

what is the acronym for classes of levers ?

Answer 11

A-R-M

Question 12

what is the acronym “A-R-M” classified according to ?

Answer 12

the relative positions of the axis, motive force and resistive force

Question 13

what is a first class lever ?

Answer 13

axis between the motive force and resistive force (MAR) (eg: see-saw)

Question 14

what are some examples in the body of a first class lever ?

Answer 14

• agonist/antagonist action
• elbow extension
• plantar flexion

Question 15

what is a second class lever ?

Answer 15

• resistance in middle (ARM)
• torque advantage usually exists for motive force

Question 16

whats more versatile? a class 1 or class 2 lever ?

Answer 16

class 1

Question 17

what is an example of class 2 lever ?

Answer 17

push up

Question 18

what is a third class lever ?

Answer 18

• motive force in middle (AMR)
• most joint complexes act as 3rd class levers
• muscle is motive force
• advantage in ROM and speed of movement but disadvantage in force
• most joint complexes are of this type

Question 19

how to remember a 1st class lever ? (acronym)

Answer 19

MAR

Question 20

how to remember a 2ND class lever ? (acronym)

Answer 20

ARM

Question 21

how to remember a 3RD class lever ? (acronym)

Answer 21

AMR

Question 22

in the acronym ARM what does the A stand for ?

Answer 22

axis of rotation (fulcrum)

Question 23

in the acronym ARM what does the R stand for ?

Answer 23

resistive force

Question 24

in the acronym ARM what does the M stand for ?

Answer 24

motive force