ens 306 final sdsu

sum of known and unknown joint forces and torques

with inverse dynamics, ΣFx and ΣFy are what values?

When you rotate about the COG

When is I the lowest?

Increase I

Moving the axis away from the COG will have what effect?

using anthropometry table

With inverse dynamics, how are m (of ΣFx), m (of ΣFy), and Iz computed?

from motion capture system

With inverse dynamics, how are ax, ay, and az computed?

radius of gyration squared

The moment of inertia about the center of gravity is calculated by multiplying the mass of the body segment by .

I(COG)

m(foot) * k^2(foot) =

d

Variable for the distance from the joint axis to the COG

linear; rotational

In a pure moment, there is no ___ effect, only a ___ effect.

0; not 0

In a pure moment, ΣF= ? and ΣT= ?

linear only

If the ΣF is unequal to 0, but ΣT = 0, what effect is produced?

equilibrium

If both ΣF and ΣT = 0, what effect is produced?

I(COG); d^2

I (segment about axis) = + [m(total) * ?]

COG

point in which all torques due to gravity sum to zero

maintain stability

What is the main goal of static balance?

COP

location of the point of application of the GRF vector

within the BOS

Where must the COP be located according to Shawny Boy?

get low, get wide, or get help (cane)

How to ensure optimal balance?

increases; lowers

Erin will be more stable if she _ her BOS and her COG

BOS

area within all lines connecting the outer perimeter of each of the points of support of an object

directly over the COP

For equilibrium to occur, where must the COG be?

COG cannot go beyond BOS

What are the limits of standing balance?

GRFy

In static standing equilibrium, ΣFy = 0 = __ - mg

GRFy = mg

Static equilibrium standing equation:

dynamic

Many _ measures are statically unstable.

falls

Dynamic balance is a series of uninterrupted __.

True (Dynamic)

(T/F): There are times when the COG may fall out of the BOS.

sequential foot placements

How is balance achieved during dynamic movement?

COP location

What is the most telling piece of information about balance?

GRFy

When restoring torque, body weight (mg) is roughly equal to what important variable?

sway distance

balance ability in inversely related to what variable?

sways; lean; falling

The less a person ___, the farther they can ___ without ___.

Kira will fall; Brooke will watch her fall

Brooke has a path length of 6 cm. Kira has a path length of 20 cm. Brooke leans over a ledge as far as she can balance herself and sees Justin Bieber. She yells for Kira to come look, and Kira leans over at the same angle. What happens to Kira? What happens to Brooke?

A person's balance ability dictates how far forward they can lean without falling. (Terrible balance trying to lean forward at the same angle as someone with good balance can't happen…. poor Kira)

Referring to the Kira-Brooke analogy, what concept is being demonstrated?

compression, tension, bending

What are the 3 types of loading?

elastic modulus;

what does the variable "y" stand for?

max stress possible

Ultimate strength is the _

There will be a new initial length defined (and she won't run in flip flops)

Brooke is running to get donuts while wearing flip flops and inverts her ankle far enough that the tissue enters the plastic region. What will result when her sprain heals?

stiffness; decrease stiffness

Increasing the elastic modulus will increase what? What will decreasing y do?

water content

Viscoelastic properties are largely do to ___ in the tissues

stress-relaxation; creep; strain-rate dependency

Name the 3 viscoelastic properties

creep

Defined as a decrease in strain when stress is held constant

stress-relaxation

Defined as a decrease is stress when strain is held constant

strain-rate dependency

mechanical properties depend on the rate of change in strain

L; L initial; time

strain rate equation: (Δ?/?)/Δ?

total stress

y * strain + (viscosity * strain rate) = ?

y; viscosity

In the total stress equation, what are the 2 material properties?

plastic region

Results in micro tears

microtears; macrotears

failure is the accumulation of __, leading to ____

margin of safety

The distance between the maximum stress capacity and the demand is known as?

increase stress max; decrease demand (stress)

What are the 2 steps to take in acute injury prevention besides bubble wrap?

time of load application; CSA

If the actual contacting force cannot be changed, decreasing the amount of stress placed on a tissue can still be done in 2 ways: Decrease _ or increase _.

impulse

decreasing the force without changing the sum of forces lies under what concept.

increase material density through exercise.

In preventing acute another acute patellar subluxation, how should Kira increase her tissues' stress max?

chronic injury; stress max decreases with increasing microtears

A constant amount of force applied often can result in what? How does this occur?

decrease frequency

What is one prevention technique unique to chronic prevention?

bone minerals per unit volume

What is bone mineral density?

compression; tension

A bone is stronger in _ than in _.

their shape

What makes bones susceptible to bending trauma?

outer bone

Where is most of the bone mineral density located?

ligaments

What holds bones together?

tensile

Ligaments resist __ loading

side; original force; final force

For__ ligament loading: cosθ= (?)/(?)

≈ ; >>

For a small angle that the ligament is placed in with a side load, Ff ____ Fo; For a large angle, Ff ___ Fo.

ACL tears

What is an example of ligament Ff >> Fo?

False (Where the force is applied matters!!)

(T/F): A force value will have an equal effect no matter where or how it is applied because the magnitude does not change.

N; a

- w = m * _

lever arm

line from the axis of rotation to the applied force

moment arm

line through the axis intersecting with force

horizontal velocity

In projectile motion, what variable is always constant?

distance traveled from projection point to landing.

The horizontal velocity is equal to the __ over the change in the time it took to get there.

false

(T/F) During an acute injury, the ultimate strength decreases during the movement.

true

(T/F) During an acute injury, the ultimate strength cannot combat an excessive force.

the force concentration

what is the elastic modulus (y)?

The force increases; strain increases

Erin's elastic modulus in her SCM is always constant. A very direct pinpointed spot on her anterior SCM fibers is struck by an athlete's foot. In order for her muscle to maintain y, what happens to all other variables?

decreased; decreased

For a constant y: an increase in area of applied force will result in a force and a _ strain.

highest ultimate strength

What is defined as the highest peak before failure?

undetermined

A more massive body segment will contribute a _ amount to the COG location compared to a less massive segment.

COG is influenced by a segment's weight and location of that weight.

A body segment's mass alone will not influence the COG location. What concept makes this true?

False (they can, but don't HAVE to)

(T/F): The highest elastic modulus and highest point of ultimate strength occur at the same time.

dynamic friction

What represents the exact amount of force applied to a sliding body?

static friction

What represents the maximum possible force needed to keep and object from moving?

False( it always points to the center)

(T/F): Centripetal acceleration only points to the center if the object is circular.

FLASE (its Tangental VELOCITY)

(T/F): Tangental acceleration is able to maintain its circular path around an object because of centripetal acceleration's pull.

Tangental velocity

What variable is perpendicular from the location of the body to the axis of rotation?

-4.7 m/s2

Tim is chasing Brooke because she stole the Gavalón from the ATR. Brooke is running at a velocity 20 m/s, while Tim is running 28 m/s and gaining on her. Then he trips and falls on his face. Brooke freaks out and sprints backward to him in 10 seconds at -27 m/s to see if he needs to activate the EAP. What is the Brooke's total acceleration?

mass; acceleration

All forces acting on an object must be related to the of said object and the _ of which the object exerts said force.

her mass and her sum of forces; time in which she applies the force

If Kira wants to increase the momentum she has when she punches her boyfriend, what two variable can she increase to do so? What should she decrease?

D

Which statement if FALSE?
A. Mechanical properties represent how a body responds to a load.
B. The material properties are "normalized" properties that state how a cross-section of
the material responds.
C. The mechanical properties are determined by the materials properties, the amount of
material, and how that material is arranged.
D. None of the above are false

Mechanical

__ properties represent how a body responds to a load.

Material

__ properties are "normalized" properties that state how a cross-section of
the material responds.

properties; amount; arrangement

The mechanical properties are determined by the _ of material, the of
material, and the ____ of material.

tension

A load that pulls the parts of a body apart is known as __.

decrease

As the distance from the neutral axis decreases during a bending load, the forces acting on the material tends to __.

strength

The amount of loading an object can withstand

elastic deformation

A deformation in which the object returns to its original dimensions after the deformation.

neutral axis

the line along which there is neither compressive nor tensile loading on a body during loading

yield point

the amount of deformation that marks the transition from elastic to plastic deformations

bending

Breaking a stick across your knee is an example of:

E

During landing from a jump, stress on the bones in the foot can be decreased by which of the following methods?
A. Decreasing the load
B. Increasing the contact surface area
C. Increasing the time over which the force is applied
D. Only A and B
E. All