REVISION Flashcards
class I lever and example
fulcrum between load force and applied load
atlanto-occipital joint = fulcrum
load = weight of skull
applied load = trapezius and splenius capitis
Class II lever and give an example
load is between applied load/effort and fulcrum
e.g metatarsophalangeal joint = fulcrum and calf muscle = applied load and body weight = force load
Class III lever and give an example
applied load is between force load and fulcrum
e.g. humeroulnar joint = fulcrum, bicep = applied load weight of forearm and wrist = load
what is mechanical advantage and why is Class II lever mechanically advantaged and Class III lever is mechanically disadvantaged
effort/force load mechanically advantaged > 1 mechanically disadvantaged < 1 torque = weight by distance greater distance between fulcrum and applied load in class II in comparison to distance between force load and fulcrum means effort can create greater torque.
newtons 2nd law
acceleration of object is directly proportional to net external force and inversely proportional to its mass
i.e the greater external net force = greater acceleration of object and greater the mass = slower acceleration
newtons 2nd law formula
F =ma
F = force
M = mass
a = acceleration
weight formula
weight x acceleration
newtons 3rd law
object exert force on another object and other object exerts force of same magnitude in opposite direction
RTA is an example of which newtons law
newtons 3rd law
force formula on Newtons 2nd law
F = ma acceleration = (v2 - v1)/t F =m(v2 - v1)/t Ft = m(v2 - v1) F = force t = time m = mass v1 = initial speed v2 = final speed increase interaction time = decreased force
precautions for RTA
seatbelts
airbags
crumple zone
how do seatbelts minimise impact force
prevents person from being propelled forward by inertia and hit the windscreen
how do airbags minimise impact force
driver comes to rest slower
air slowly pushes out of bag
more interaction time against bag less impact force
how do crumple zone reduce injury
as the car distorts it increases interaction time
reduces impact force
energy definition
ability to do work
work definition
force x distance
work energy principle
total mechanical energy = kinetic energy + potential energy
total mechanical energy @ start = total mechanical energy +/- work done
power
work done/time
rate of energy expenditure
efficiency
work done/ energy expenditure
stress
sectional area subjected to a force
Force / Area
types of stress
compression
tension
torsion
shear
strain
stress results in change in length
change in length / length
strain example
tension
compression
youngs modulus
stress / strain
describe graph of stress y axis and strain x axis
A to B - return to original length = elastic deformation B to D - plastic deformation permanent change in length
beyond B = beyond elastic limit
point C = permanently deformed, maximal permissable stress
point D - fracture
describe the biomechanical forces in the bone that resist bending
top surface of the bone in tension tries to ‘pull’ surface back to original shape
bottom surface ‘push’ molecules back to original shape under compression
hollow bone = more resistance in bending
precautions to prevent low back pain
maintain good posture and natural curvature of spine - to prevent crushed vertebrae
feet apart = increased bos Knees bent
centre of gravity definition
single point that moves in accordance with newtons simple laws of motion
how does cog influence amputees balanced
COG is between 2 legs
has torques of equal magnitude in opposite direction and cancel each other out
COG is shifted and torque is unbalanced
patient is unstable and wobbles
unit for charge
coloumb
unit for current
amperes
unit for voltage
volt
unit for resistance
ohms
coloumb force =
force = constant(Q1.Q2)/r2
static electricity
build up of charge that attract and repel excess charge
safety hazard of static electricity
sparking - presence of flammable liquids
lack of humidity
precautions for build up of static electricity
humidifiers - moisture in the air drain excess charge by attracting water molecules
anti static flooring and rubber for masks
surgical gowns treated with silicone
all electrotherapy or ICU equipment should be earthed
Ohm’s law and how it influences physiological response to electric current
V = IR
V = voltage
I = current
R = resistance
resistance is inversely proportional to current
wet skin - less resistance - more current
components in a delivery system
diathermy unit active cable active electrode dispersive plate dispersive cable
purpose of dispersive plate
to disperse RF current and prevent thermal injury
microshock sensitive patients why that is dangerous
pacemakers
catheters
internally placed conductor
internal electrical path directly to heart
precautions for microshock sensitive patients
patient should not be grounded - path directly through patient and into heart that can lead to fibrillation and as it disperses infintely throughout the ground
all equipment connected or near the patient should be earthed - provides path for electric current to go down to earth without going through patient
Joule’s law
E = I^2Rt E = energy I = current R =resistance t = time currently passed directly thru = tissue heating up
components of circuit in short wave therapy
main power supply - high frequency generator and amplifier
oscillator coil
resonator coil
variable capacitor
Physiological effects of SWT are those of heat in general
Tissue Temperature Increase Increased Blood Flow (Vasodilation) Increased Venous and Lymphatic Flow Increased Metabolism Changes In Physical Properties of Tissues Muscle Relaxation Analgesia
how ions respond to SWT
High frequency current - > ions accelerated along the lines of electric field.
- the ions to oscillate (or vibrate) about a mean position by oscillating electric field
- The ions kinetic energy is converted to heat.
How dipolar molecules respond to SWT
High frequency current -> rotation of the Dipolar (sometimes referred to as simply polar) molecules.
- the molecules will rotate at the same frequency as the e-m radiation
Moderately efficient heating occurs because of the frictional drag between the molecules.
how non polar molecules respond to SWT
The paths of the orbiting electrons become distorted, first in one direction, then in the other as the electric field oscillates.
Capacitive method of SWT
Where the patient (tissue) is placed between the two electrodes, essentially acting like a capacitor
Inductive method of SWT
The variable capacitor in the ‘patient circuit’ is connected in parallel with another inductance coil mounted in a single pad or electrode
The rise in tissue temperature associated with the application of SWT depends on a factor known as
the Specific Absorption Rate Watts/kg
