Biomechanical principles

Question 1

Newton’s laws

Answer 1

First law - law of inertia
second law - law of acceleration
third law- law of action - reaction

Question 2

law of inertia

Answer 2

• inertia - disinclination to change direction or speed
• remains at rest unless acted upon - resists change in motion (wants to stay in equilibrium)

Question 3

law of acceleration

Answer 3

• acceleration is inversely proportional to the mass of the body

Question 4

law of acceleration equation

Answer 4

F= ma and a= F/m

Question 5

law of action - reaction

Answer 5

always an equal and opposite reaction to any reaction

Question 6

increase of force results an increase of

Answer 6

acceleration

Question 7

increase of mass results an decrease of

Answer 7

acceleration

Question 8

linear

Answer 8

inertia: energy required to alter linear velocity
- directly proportional to its mass

Question 9

inertia

Answer 9

resistance to change in linear velocity ( a force is required to start, stop, slow, speed up, or alter direction of linear motion)
- measured by amount of energy required to change linear velocity

Question 10

Angular

Answer 10

mass moment of inertia (I)
- energy required to alter angular velocity
- depends on mass and mass distribution

Question 11

mass moment of inertia

Answer 11

resistance to change in angular velocity ( a torque is required to start, stop, slow down, speed up, or alter rotational motion)
- decrease moment arm = increase speed

Question 12

balance

Answer 12

Center of Mass (COM) = center of gravity (COG)

Question 13

COM

Answer 13

point about which body’s mass is evenly distributed (average location of mass distribution)

Question 14

COG

Answer 14

point about which effects of gravity are completely balanced (the point about which the net torque due to gravity is zero)
- vertical projection of COM to the ground

Question 15

true or false: as the mass changes its distribution, mass moments of inertia changes

Answer 15

true

Question 16

true or false: as the mass moment of inertia increases, it chases faster rotation

Answer 16

false: slower rotation

Question 17

true or false: to stay upright, we have to keep our COG within out Base of support (BOS)

Answer 17

true

Question 18

BOS

Answer 18

is the footprint of all paths of the body in contact with the ground

Question 19

how do we prevent falls?

Answer 19

control the inertia and BOS
- AD widens the BOS (easier to keep COG within it)
- stepping strategy

Question 20

true or false: a mass closer to the ground makes it more difficult for an external force to change the mass moment of inertia

Answer 20

true: shorter moment arm for the force action on the COM

Question 21

suspension strategy

Answer 21

bringing COM closer to the ground

Question 22

Linear acceleration equation

Answer 22

f = ma
a = F/m

Question 23

angular acceleration equation

Answer 23

T= Ia
a= T/I

Question 24

linear acceleartion

Answer 24

a body is directly proportional to the force (F) causing it inversely proportional to its mass (m), and it occurs in same direction as the force causing it

Question 25

angular acceleration

Answer 25

directly proportional to the torque causing it (T), and inversely proportional to the mass moment of inertia (I). occurs in same rotatory direction as the torque causing it

Question 26

true or false: torque is independent on moment arm and force

Answer 26

false: torque is dependent on moment arm and force

Question 27

Troque equation

Answer 27

T = F x MA (moment arm)

Question 28

another equation for torque

Answer 28

T = I x angular acceleration (alpha symbol)

Question 29

true or false: increasing the force or the MA will increase the energy required to accelerate the leg (increase mass moment of inertia)

Answer 29

true

Question 30

mommentum

Answer 30

quantity of motion possessed by a body

Question 31

impulse

Answer 31

a force applied over a period of time

Question 32

Impulse/momentum relationship equation

Answer 32

F x t = m x Change in velocity

Question 33

F x t = m x Change in velocity same as

Answer 33

T x t = I x change in angular velocity

Question 34

applying force slowly = time increases =

Answer 34

effect of body decrease

Question 35

work

Answer 35

change in kinetic energy caused by a force applied over a given displacement

Question 36

work equaation

Answer 36

w = F x d work = force times distance

Question 37

power

Answer 37

amount of work done over a g given duration

Question 38

power equation

Answer 38

P = W / t power = weight over time

Question 39

to increase rate of work (power), you must

Answer 39

decrease time or increase work

Question 40

3rd law of again and reaction

Answer 40

opposite and equal reaction - GRF - joint reaction forces -single impact vs cumulative impact (stress factor)