Lecture 3

Question 1

When does equilibrium happen?

Answer 1

this exist when object are at rest where all the F acting upon a body are balanced

Question 2

What is a lever

Answer 2

• simple machine
• elongated, ridig object
• rotates around fixed point ( axis)
• has ability to change sped, distance, direction of applied force, force strength

Question 3

What is an effort of a lever

Answer 3

this is a force applied to one point

Question 4

what is a resistance

Answer 4

this is the load located at some other point

Question 5

what is the effort arm

Answer 5

part of the lever from axis to point of effort or F

Question 6

what is the resistance arm

Answer 6

part of lever from axis to point of resistance or load

Question 7

when will movement happen?

Answer 7

this will occur when effort exceeds resistance

Question 8

What is a 1st class lever

Answer 8

effort —–axis—— load

• axis is always in the middle
• can create a balance
• see saw

Question 9

what is a 2nd class lever

Answer 9

axis——load——-effort

• the lad will also be closer to the axis
• will over come a large resistance
• wheel barrow

Question 10

what is a 3rd class lever

Answer 10

axis—-effort—– load

• effor arm will always be shorter than load arm
• ↑ ROM and ↑ speed
• your arm
• the most in the human body

Question 11

what is dynamic equilibrium

Answer 11

bodies in motion with all acting forces resulting in equal and oppositely directed inertial f

• sum F(x) -ma(x)=0
• sum F(y) -ma(y)=0
• sum T(G) - ix=0

Question 12

what is stability

Answer 12

resistance to both linear and angular acceleration. so basically resistance to disruption of equilibrium

Question 13

what is balance

Answer 13

ability to control equilibrium

Question 14

what is center of gravity

Answer 14

the point aroudn which a body weight is equally balanced in all direction

Question 15

what is the line of gravity

Answer 15

vector from the COG vertically downward toward the center of the earth

Question 16

what is the base of support

Answer 16

area bound by the outermost regions of contact between a body and the support surface
(if your line of gravity in the base of support you will be stable)

Question 17

what can increase a bodys stability

Answer 17

↑ body mass
↑ Fr btwn the body and the surface of contact
↑ the size of the bos in the direction of an external force
-horizontally position the COG near the edge of the BOS on the side of the external force
-vertically positioning the COG as low as possible

Question 18

what is stress

Answer 18

external force on body are resisted by internal forces

Question 19

what is strain

Answer 19

external forces that caused deformation of tissue

-deformation will all depend on the tissue

Question 20

what is Tension

Answer 20

occur at analysis plane and result of force that tends to pull apart molecules that bond object together

• act L to analysis plane
• Stress= F/A

Question 21

What is compression

Answer 21

axial stress that tends to push molecules together

Question 22

what is shear

Answer 22

this act parallel to analysis plane

- tends to slide molecule past each other

Question 23

what is bending

Answer 23

this will produce different stresses at analysis plan

• will have deformation by curving
• • tension on the elongating side
• • compression on the shorten side

Question 24

what is torsion

Answer 24

occurs when torques act about the long axis of an object and has shear force btwn molecule of left/ right side of analysis plane

Question 25

what is stiffness

Answer 25

ration of stress/strain in a loaded material | -- this is the extent to whcih it resists deformation in response to an applied force

Question 26

what is the yield point

Answer 26

is the point the stress strain curve where additional stress will cause permanent change

Question 27

what is toughness

Answer 27

ability of tissue to absorb energy

Question 28

what is collagen

Answer 28

- fibrous protein - most in connective tissue - the arrangement provide low failute strain and high tensile strenght - BUT unable to resist compression

Question 29

what is Bone

Answer 29

- absorbs majority of compression - -30-35% collagen - -1-2% ground substance - -45% mineral - -20% water - -- how health and how well it works depends on age and health - BUT weakest in shear

Question 30

what are the 3 types of cartilage

Answer 30

1 hyaline cartilage- best at compression 2 fibrocartilage- compression and tension 3 elastic cartilage- more elastic

Question 31

What are tendon and ligaments

Answer 31

--70% water --25% collagen --5% groudn substance fibers are // or nearly // to the functional axis ** ligs are more elastic then tendons *** ligs have high tensile strength but no compression or shear and are weaker than tendons

Question 32

what are the 2 component of a muscle

Answer 32

Active- contraction determines stiffness | Passive- muscle stretched

Question 33

what is Parallel elastic component

Answer 33

passive elasticity derived from muscle membranes

Question 34

what is series elastic component

Answer 34

acts as a spring to store elastic energy in tendons

Question 35

what is concentric

Answer 35

involving shortening

Question 36

what is eccentric

Answer 36

involving lengthening

Question 37

what is isometric

Answer 37

involving no change

Question 38

what are parallel fibers of a muscle

Answer 38

they are // with the longitudinal axis of the muscle. doesnt have to extend the whole muscle - PCAS= small (force producing ability) - Force=small - ROM=large

Question 39

what are pennate fiber of a muscle

Answer 39

lie at an angle to the longitudinal axis of the muscle and attaching to the tendon and will extend the entire length of the muscle ** the angle of the pennation ↑ as tension ↑ in the muscle - PCSA= huge (force producing ability) - Force= huge - ROM= small

Question 40

force - velocity relationship

Answer 40

look at graph in slides page 5 (3b)

Question 41

what is stretch- shortening cycle

Answer 41

actively tensed muscle that is stretched just prior to contraction result in a more forceful contraction than the absence of the prestetch **think of the reason you bend down before you jump

Question 42

what are some factors that affect muscular strength

Answer 42

tension generating | moment arms

Question 43

what is tension generating

Answer 43

capability of the mscle tissue whcih is in turn affected by - -muscle cross section area - - training state of muscle

Question 44

what is moment arms

Answer 44

they are the muscle crossing the joint in turn affected by: - -distance btwn muscle attache to bone and joint center - - angle of the muscle attachment to bone

Question 45

muscular strength

Answer 45

read the last slide on 3b page 6

Question 46

equation for linear strain

Answer 46

e= change in length/ original length

Question 47

equation for elastic

Answer 47

E= change in stress / change in strain