Forces

Question 1

simply defined, a force is ? and comes in pairs of ?

Answer 1

push or pull, action and reaction

Question 2

1 N of force is the the force required to accelerate?

Answer 2

1 kg of mass @ 1 m/s^2

Question 3

2 types of internal forces

Answer 3

• compressive = pushing

- tensile = pulling

Question 4

what can be used inside cadaver joints to measure forces for injury prevention

Answer 4

strain gauge

Question 5

2 types of external forces

Answer 5

• contact (solid, fluid, air resistance, water resistance)

- non contact (gravity, magnetic, electrical)

Question 6

the magnitude of attraction of gravity depends on?

Answer 6

• the mass and distance between, of objects

Question 7

equation for force of gravity

Answer 7

• GMeMm/r^2

Question 8

4 types of strain guages

Answer 8

• force transducers (force plates, load cells)
• springs
• peizoelectric crystals
• dynamometer

Question 9

hand held dynamometers can be used to measure ?

Answer 9

• muscle strength capabilities

- weaknesses

Question 10

what is considered the gold standard for measure internal forcers

Answer 10

force plate and instrumental treadmill

Question 11

2 cons of the force plate and instrumental treadmill

Answer 11

• difficult to use in the field

- does not measure foot pressure distribution

Question 12

the equation for pressure

Answer 12

P= Force/ Area

Question 13

the most common pressure sensors work by using the?

Answer 13

piezoresistive effect, the change in electrical resistivity of a semiconductor or metal when mechanical strain is applied

Question 14

cons of pressure sensors on feet

Answer 14

• unidimensional (vertical loading only)- degree of accuracy requires refinement/ testing
• -> wearing them you may change the way you walk

Question 15

the F scan foot pressure system quantifies ?

Answer 15

force, contact pressure distribution and timing

high resolution

Question 16

during forefoot running the knee is more ? the ankle more ? and the hip is in greater ? than in heel strike running

Answer 16

• extended, plantarflexed, extension

Question 17

in a minimalist shoe, plantar pressure was higher where and lower where

Answer 17

higher fore foot, lower heal pressure

Question 18

the instantaneous point of application of the ground rxn force

Answer 18

center pf pressure

Question 19

pronation =

supination =

Answer 19

eversion (inward roll of ankle)

inversion (outward roll of ankle)

Question 20

over pronation can cause?

Answer 20

• unnecessary stress on the ankle, internal rotation of the leg at the hip and forward pelvic tilt

Question 21

some things that happen with fatigue

Answer 21

• increase pronation,
• increase loading on forefoot, midfoot, medial heel
• increased eversion

Question 22

plantar pressure measurement provide accurate ? of kinematics and location of ? on end point effector

Answer 22

timing, force

Question 23

plantar pressure systems can indicate difference in pressure distribution which can be an indicator of? (3)

Answer 23

1. performance change
2. fatigue
3. injury potential

Question 24

2 methods to approximate internal forces at the bones, tendons and joints

Answer 24

1. inverse dynamics (using external forces to guess internal forces)
2. electromyography