elasticity
DESCRIPTION
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. Stress. The average amount of force exerted per unit area - PowerPoint PPT PresentationTRANSCRIPT
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ELASTICITY
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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 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
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HOOKE'S LAWDefinition –
stress applied to a material is proportional to the strain on that material
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Hooke's law states that Where F = - k x 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.
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K = k1 + k2 Distance X = x1 +
x2
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
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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
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RUBBER ELASTIC
Thera tube & bandThe resistance provided by a Latex Band is ideal for targeting and working specific muscle groups and tendons during rehab and sports training
Common ConditionsTennis elbow (lateral epicondylitis)Ankle sprainDislocated shoulderTibialis Posterior tendon problems
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Tubigrip – compression bandages Treatment of sports and soft tissue
injuries 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.
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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
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HYDROTHERAPY
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HYDROSTATIC PRESSUREo The pressure exerted by a fluid at
equilibrium at a given point within the fluid, due to the force of gravity.
o Hydrostatic pressure increases in proportion to depth measured from the surface because of the increasing weight of fluid exerting downward force from above
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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
If this pressure gradient arises from gravity, the net force is in the vertical direction opposite that of the gravitational forc
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 HYDROTHERAPYCharacteristics 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
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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
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