kinetics

Question 1

kinematics vs kinetics

Answer 1

kinematics = describes motion w/o regard for mass/ forces
kinetics = forces that produce/ stop/ modify motion

Question 2

5 variables that determine and describe motion:

Answer 2

1. type
2. location
3. magnitude
4. direction
5. rate of motion or rate of change

Question 3

2 types of motion:

Answer 3

1. translatory/ linear = all parts travel same disrance in the same period of time in the same direction
2. rotary = every point moves about a pivot/ axis of rotation

Question 4

how is the magnitude of motion measured for each type?

Answer 4

1. linear distance = meters/ feet
2. rotary distance = degrees
   –> ROM

Question 5

distance:

Answer 5

how far a force moves a body

Question 6

how is location of motion described?

Answer 6

arounds axes (AP, ML, SI aka longitudinal)

Question 7

how is direction of motion described for rotary motion?

Answer 7

1. about medial-lateral axis = sagittal plane - flexion/extension
2. about anterior-posterior axis = frontal plane - abduction/adduction
3. about superior-inferior axis = transverse plane - medial/lateral rotation
   **except thumb, ankle, clavicle

Question 8

how is direction of motion described for translatory/linear motion?

Answer 8

according to axis AND + or -

Question 9

how can rate and change of motion be described (3)?

Answer 9

1. velocity = rate at which motion occurs
2. acceleration = rate at which velocity changes
3. torque = motion occurring about an axis

Question 10

4 types of forces that affect body motion:

Answer 10

1. gravity - 9.81m/s^2
2. muscles - contraction, stretching
3. external resistance - muscles work against
4. friction - opposes contact force, primarily responsible for human movement

Question 11

mass vs weight

Answer 11

mass = amount of matter something contains, measured w balance comparing known matter to unknown amount of matter
weight = pull of gravity on mass (mg) measure on a scale

Question 12

moment:

Answer 12

force acting at a distance from axis
M = d x F

Question 13

newtons 1st law:

Answer 13

law of inertia - body at rest/motion will stay at rest/motion until acted on by external net force
sumF = 0

Question 14

newtons 2nd law:

Answer 14

law of mass/ acceleration
F = ma

Question 15

newtons 3rd law:

Answer 15

law of action/ reaction - for every action force there is an equal and opposite reaction force

Question 16

3 elements of a lever:

Answer 16

1. axis/ fixed point
2. resistance force (R)
3. moving/ effort force (F)

Question 17

resistance arm:

Answer 17

perpendicular distance from axis to line of action of resistance

Question 18

force arm:

Answer 18

perpendicular distance from axis to moving force

Question 19

first class lever:

Answer 19

• seesaw (axis b/n force and resistance arm)
  ex: C1 = skull sitting on first vertebra
• poor mechanical advantage as muscle must generate a lot of force to overcome R

Question 20

second class lever:

Answer 20

• wheelbarrow (axis at end, force arm > resistance arm)
  ex: achilles tendon relative to toes
• mechanical advantage bc long F arm

Question 21

third class lever:

Answer 21

• bicep curl w dumbbell (most common in body)
• poor mechanical advantage = force arm is smaller than resistance arm
• can move small weight long distance

Question 22

mechanical advantage:
equation:

Answer 22

ratio b/n length of F and R arms
MA = (force arm length)/(resistance arm length)

Question 23

what can MA ratios be?

Answer 23

> 1
<1
= 1 (no advantage, F arm length=R arm length)

Question 24

how can you increase MA?
practical example:

Answer 24

increase length of the force lever
ex: closer to person = shorter resistance arm

Question 25

torque:

Answer 25

force applied around a joint/axis T= F x d (so smaller moment arm, the less torque generated)

Question 26

what happens when the angle b/n forces increases? what does it mean when angle = 0?

Answer 26

resultant force decreases = forces are in line w eachother

Question 27

COG or COM:

Answer 27

- point about which mass of object is balanced/ concentrated - a few finger widths below belly button ***exceptions: pregnancy, wider pelvis

Question 28

stable equilibrium

Answer 28

body returns t0 former position after light perturbation

Question 29

unstable equilibrium

Answer 29

body seeks new position after light perturbation

Question 30

neutral equilibrium

Answer 30

COG displaced but remains at same level ex: person in wheelchair

Question 31

when in a form of equilibrium, what does the degree of stability depend on (4) ?

Answer 31

- height of center of gravity above base of support - size of base of support - location of gravity line w/n base of support - body weight

Question 32

base of support (BOS):

Answer 32

when body is stable, line of gravity passes through center of BOS larger BOS = more stable the object is

Question 33

can small changes in muscle length create angular displacements?

Answer 33

yes

Question 34

what does the amount of force a muscle must exert to overcome external resistance depend on?

Answer 34

lever arm length

Question 35

are the body's levers designed more for speed or strength?

Answer 35

speed (most lever systems in body are third class)

Question 36

when does max resistance torque occur?

Answer 36

when segment is horizontal/ perpendicular distance to axis is greatest

Question 37

single fixed pulley: mechanical advantage?

Answer 37

- dont provide a mechanical advantage - change direction of a force ex: cable machine

Question 38

moveable pulley: mechanical advantage?

Answer 38

- provide mechanical advantage - pulley rope must be pulled twice the distance that weight is raised ex: leg traction system

Question 39

anatomical pulleys: mechanical advantage?

Answer 39

- change course of tendon - increase mechanical advantage = move tendon further from axis of rotation ex: patella

Question 40

leverage factor:

Answer 40

- use principle of leverage to increase effect on an applied force; mechanical advantage = magnifies force + move object w less effort ex: therapist position relative to client when doing muscle testing - increase effective speed of movement w a given force ex: golf swing

Question 41

stretching vs joint mobilization:

Answer 41

stretching a joint = external forces applied distally resulting in high stresses to articular tissues joint mobilization = external force applied proximally, recreate arthrokinematics while minimizing stress to articular tissues