The Kinematics of Trauma

doutfanaticalMechanics

Nov 14, 2013 (3 years and 10 months ago)

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The Kinematics of Trauma

Physics, light on the math

Axiomata sive leges motus


Lex I: Corpus omne perseverare in statu suo
quiescendi vel movendi uniformiter in directum,
nisi quatenus a viribus impressis cogitur statum
illum mutare.



Lex II: Mutationem motus proportionalem esse
vi motrici impressae, et fieri secundum lineam
rectam qua vis illa imprimitur.


Lex III: Actioni contrariam semper et æqualem
esse reactionem: sive corporum duorum
actiones in se mutuo semper esse æquales et in
partes contrarias dirigi.


Definitions and Simplifications


Dynamics


An approach to physics that involves
mathematical calculations to understand the
motion of bodies. Answers are quantitative.



Kinematics


An approach to physics that aims to
understand the motion of bodies with minimal
math. “Goldilocks physics”

Definitions and Simplifications


Mass=amount of matter


Force=push or pull


Velocity=distance/time


Acceleration=change in velocity/time


Weight=mass x gravitational acceleration


Energy=the ability to do work


Definitions and Simplifications


weight
≈mass


Density=mass/volume


Higher density=higher energy transfer




Newton’s Laws of motion


Objects in motion will stay in motion, and
objects at rest will stay at rest unless
acted on by an external force. (Inertia)


Newton’s Laws of motion


Inertia


Measured by an object’s momentum


Momentum = mass x velocity


Used to describe an object’s resistance to
changes in motion


Newton’s Laws of motion


An object’s acceleration is proportional to
the force applied, and inversely
proportional to its mass.

(Force = mass x acceleration)


Moving objects that are decelerated rapidly
exert large forces


Newton’s Laws of motion


Every action has an equal and opposite
reaction (forces exist in pairs)


The reaction may cause further actions


Forces can begin in a straight line, and
disperse, causing cavitations




Forces that cause trauma


Compression (in
-
line)


Contusions


Penetrations


Lacerations(in combination with friction)



Dislocations


Fractures



Forces that cause trauma


Torsion (rotational)


Dislocations


Fractures



Forces that cause trauma


Friction (tangential)


Abrasions


Lacerations(in combination with compression)


What injuries do you expect?


Small group collaboration


Think of as many injuries as you can.


Compression Injuries?


Torsion Injuries?


Friction Injuries?


Include type and location


Explain where the forces involved
originated

Pressure


Pressure = Force / Area


Pressure determines whether trauma is
blunt or penetrating


Energy


Can not be created or destroyed, only
transferred or transformed


Types of Energy


Thermal


Electromagnetic


Chemical


Mechanical



Injuries by energy type


Electrical energy transforms into heat based on
resistance to current flow.


Heat energy does work on cells by denaturing
proteins and vaporizing intracellular water.


Chemical energy denatures proteins, and can
transform into heat energy in the process.


Mechanical energy does work on body structures
by changing their position.


Electromagnetic Energy


Voltage is the “push” behind electricity.


Current is the amount of electricity.


Aside from the nervous system, the
human body is not a good conductor.


High resistance means lots of energy
transformed into heat.


Thermal Energy


The human body is 70% water on average


As water is changed to steam, it increases
in volume 1700 times


Protein denaturing= irreversible changes
in chemical structure.



Chemical energy


Most chemical burns are due to extreme
pH.


Acids donate protons


Bases steal protons


Too many or too few protons leads to
protein denaturation.

Mechanical Energy


Two components: kinetic and potential


Kinetic is the energy of motion:





Potential is stored energy due to height




height
gravity
mass


2
2
velocity
mass

Energy Relationships


In any system, the mechanical energy is
the sum of the potential and kinetic
energies.


Decreasing potential energy (falling) means
increasing kinetic energy.

Energy Relationships


Work and Energy are equivalent




W=E


W=Fd


F=E/d


Energy transfer


Radiation


Conduction


Convection


Work


What’s it all mean?


Since velocity is
squared:


Doubling speed = 4x
force


Tripling speed = 9x
force


Stopping distance:


Shorter distances
mean greater forces

0
1000
2000
3000
4000
5000
6000
7000
1
5
10
20
40
80
Speed
Kinetic Energy
0
5
10
15
20
25
30
35
100
50
25
12
6
3
Stopping distance
Force exerted
Anatomical Concerns


Most organs are not well secured within
the body.


Heart, kidneys and liver have massive blood
supply


Anatomic Concerns


Sudden shifts can shear the vessels
connected to these organs


Blunt trauma to these organs can cause
massive contusions


Penetrating trauma to these organs can
cause life threatening loss of blood

Anatomical Concerns


Brain floats inside a boney cage



A sudden shift stops the skull first, which then
stops the brain


Vasculature on the surface of the brain is
extensive


As intracranial space fills with blood, where
will it go?


Brain Vasculature

Anatomical Concerns


Fragile body parts


Lungs are only a single cell thick


Sudden impact can cause “paper bag” effect


Spleen and liver covered only with a thin layer
of connective tissue


Contusions and ruptures common


GI tract is a series of “bags”


Anatomical Concerns


Spinal curvature


Cervical and
Sacral lordosis


Thoracic kyphosis


Forces can alter
these curvatures


Special Considerations


Some situations may:


Alter the normal mechanics of the body


Cause multiple phases of injury


Pneumothorax


Breathing is accomplished by creating
“negative pressure”


Diaphragm contracts, reducing the
pressure in the chest


Air rushes in to equalize the pressure


Holes in the lung or chest wall allow air
into the chest cavity, rather than the lung

Blast Injuries


Primary from absorbing the energy of the
blast


Secondary from being hit with flying
objects


Tertiary from being thrown against
stationary objects

Motor Vehicle Collisions


Two systems of vehicle plus passengers


Total energy is the sum of the energies of
the vehicles plus passengers


Energy is transferred from vehicle to
vehicle, and between passengers and
vehicles.

Fall from height


Longer falls mean more kinetic energy


Terminal velocity reached at about 60 ft.


Elastic surfaces will absorb some of the
energy of the falling person


Inelastic surfaces cause ALL of the energy
of the fall to be absorbed by the body


QUIZ!

Let’s see what stuck.


Please email your answers to:


cmehl@sheridanmemorial.net

Question 1


How many laws of motion did Isaac
Newton posit?


Question 2


Which object has greater momentum?


A speeding bullet


A fully loaded ambulance at 10 mph


Question 3


List a type of injury that could be caused
by each of the following:


Compressional Force


Torsional Force


Frictional Force


Question 4


Which of the following is true regarding
the magnitude of the forces involved in a
vehicle collision?

A.
The mass of the vehicle is more important
than the speed

B.
The mass of the vehicle is less important
than the speed

C.
The area of collision matters the most

D.
Airbag deployment matters the most


Question 5


Which seatbelt will reduce the force of
impact best?

A.
A seatbelt that does not flex

B.
A flexible seatbelt that stretches slightly

C.
No seatbelt


Question 6


What are the three causes of injury from
explosions?

Question 7


How is it possible for electricity to cause
burns?

Question 8


What determines whether an injury will
be blunt or penetrating?


Question 9


Energy cannot be __________________
or ___________________, only
________________ or ______________.


Question 10


Why are motor vehicle collisions so
damaging to the human body?


Please email your answers to:


cmehl@sheridanmemorial.net