Transcript elasticity

ELASTICITY
WHAT IS AN ELASTICITY?
Measurement of the percentage change in one
variable that results from a 1% change in
another variable.
 Can come up with many elasticity's.
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STRESS
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The average amount of force exerted
per unit area
It is the internal resistance a material
offers to being deformed and is measured
in terms of the applied load
HOOKE'S LAW
 Definition
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stress applied to a material is
proportional to the strain on that
material
Hooke's law states that
 Where
F=-kx
 x is the displacement of the spring's end from its
equilibrium position (a distance, in SI units: meters)
 F is the restoring force exerted by the spring on that
end (in SI units: N or kg·m·s-2)
 k is a constant called the rate or spring constant (in SI
units: N·m-1 or kg·s-2)
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Hooke's law only holds for some materials under
certain loading conditions
Steel exhibits linear-elastic behavior
Hooke's law is valid for it throughout its elastic
range
Rubber is generally regarded as a "non-hookean"
material because its elasticity is stress dependent and
sensitive to temperature and loading rate.
Applications of the law include spring operated
weighing machines, stress analysis and modelling of
materials.
K = k1 + k2
 Distance X = x1 + x2
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1/K = 1/k1 + 1/k2
 X1/x2 = k2/k1
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Hooks law is valid in the O – P level
Elastic limit - material no longer go back to its
original shape when the load is removed
Yield point - Yield point is the point at which the
material will have an appreciable elongation or
yielding without any increase in load
Rapture strength is the strength of the material
at rupture. This is also known as the breaking
strength
ELASTIC MATERIALS USED IN
PHYSIOTHERAPY
Springs
 Rubber elastic
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SPRINGS
 Elastics
object used to store mechanical energy
 Springs are usually made out of spring steel
 Spring is compressed or stretched, the force it
exerts is proportional to its change in length
RUBBER ELASTIC
Thera tube & band
The resistance provided by a Latex Band is ideal for targeting
and working specific muscle groups and tendons during rehab
and sports training
 Common Conditions
Tennis elbow (lateral epicondylitis)
Ankle sprain
Dislocated shoulder
Tibialis Posterior tendon problems
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Tubigrip – compression bandages
Treatment of sports and soft tissue injuries
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Provides tissue support in the treatment of
sprains and strains, sports injuries, general
oedema, post- burn scarring and ribcage
injuries and is also used for pressure dressings
and arm fixation
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Tubigrip is an excellent compression
option for implementing the R I C E
regime for sports and soft tissue injuries
in the acute or inflammatory phase.
Knee guard
 Not be for long-term daily wear as this will weaken
knee muscles
 Knee support should be used as a temporary measure
to manage your knee discomfort until professional
advice is sought
HYDROTHERAPY
HYDROSTATIC PRESSURE
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The pressure exerted by a fluid at
equilibrium at a given point within the
fluid, due to the force of gravity.
Hydrostatic pressure increases in
proportion to depth measured from the
surface because of the increasing weight
of fluid exerting downward force from
above
BUOYANCY
Any body of arbitrary shape which is
immersed, partly or fully, in a fluid will
experience the action of a net force in the
opposite direction of the local pressure
gradient
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If this pressure gradient arises from
gravity, the net force is in the vertical direction
opposite that of the gravitational forc
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This vertical force is termed buoyancy and
is equal in magnitude, but opposite in
direction, to the weight of the displaced fluid
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HYDRODYNAMIC PRINCIPALS OF
HYDROTHERAPY
 Characteristics
of water
Mass, weight, density, specific gravity, buoyancy,
hydrostatic pressure, surface tension
Turbulance
Any mvt creates turbulance it can assist as well as
resist mvt
Laminar flow
 Turbulent flow
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Help with many physical and emotional complaints,
including:
Back pain,
Rheumatic pain and arthritis,
Anxiety and stress,
Poor muscle, poor circulation, muscle pain and
inflammation,
Hip or other joint replacements (before and
after the operations),
Muscle or ligament injuries; broken limbs
Neurological conditions such as strokes or
brain injuries