1. The Kinematics of Trauma
Physics, light on the math

2. 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.

3. 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”

4. 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

5. Definitions and Simplifications
weight≈mass
Density=mass/volume
Higher density=higher energy transfer

6. 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)

7. 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

8. 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

9. 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

10. Forces that cause trauma
Compression (in-line)
Contusions
Penetrations
Lacerations(in combination with friction)
Dislocations
Fractures

11. Forces that cause trauma
Torsion (rotational)
Dislocations
Fractures

12. Forces that cause trauma
Friction (tangential)
Abrasions
Lacerations(in combination with compression)

13. 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

14. Pressure Pressure = Force / Area
Pressure determines whether trauma is blunt or penetrating

15. Energy
Can not be created or destroyed, only transferred or transformed
Types of Energy
Thermal
Electromagnetic
Chemical
Mechanical

16. 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.

17. 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.

18. 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.

19. 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.

20. Mechanical Energy Two components: kinetic and potential
Kinetic is the energy of motion:
Potential is stored energy due to height

21. 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.

22. Energy Relationships Work and Energy are equivalent Energy transfer
W=E
W=Fd
F=E/d
Energy transfer
Radiation
Conduction
Convection
Work

23. What’s it all mean? Since velocity is squared: Stopping distance:
Doubling speed = 4x force
Tripling speed = 9x force
Stopping distance:
Shorter distances mean greater forces

24. Anatomical Concerns Most organs are not well secured within the body.
Heart, kidneys and liver have massive blood supply

25. 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

26. 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?

27. Brain Vasculature

28. 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”

29. Anatomical Concerns Spinal curvature Forces can alter these curvatures
Cervical and Sacral lordosis
Thoracic kyphosis
Forces can alter these curvatures

30. Special Considerations
Some situations may:
Alter the normal mechanics of the body
Cause multiple phases of injury

31. 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

32. Blast Injuries Primary from absorbing the energy of the blast
Secondary from being hit with flying objects
Tertiary from being thrown against stationary objects

33. 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.

34. 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

35. Please email your answers to:
QUIZ!
Let’s see what stuck.
Please your answers to:

36. Question 1
How many laws of motion did Isaac Newton posit?

37. Question 2 Which object has greater momentum? A speeding bullet
A fully loaded ambulance at 10 mph

38. Question 3
List a type of injury that could be caused by each of the following:
Compressional Force
Torsional Force
Frictional Force

39. Question 4
Which of the following is true regarding the magnitude of the forces involved in a vehicle collision?
The mass of the vehicle is more important than the speed
The mass of the vehicle is less important than the speed
The area of collision matters the most
Airbag deployment matters the most

40. Question 5 Which seatbelt will reduce the force of impact best?
A seatbelt that does not flex
A flexible seatbelt that stretches slightly
No seatbelt

41. Question 6
What are the three causes of injury from explosions?

42. Question 7
How is it possible for electricity to cause burns?

43. Question 8
What determines whether an injury will be blunt or penetrating?

44. Question 9
Energy cannot be __________________ or ___________________, only ________________ or ______________.

45. Question 10
Why are motor vehicle collisions so damaging to the human body?

46. Please email your answers to: