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Elasticity - PowerPoint PPT Presentation

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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

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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.


  • 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 –

    stress applied to a material is proportional to the strain on that material

Hooke's law states that

  • WhereF = - 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)

  • 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

  • 1/K = 1/k1 + 1/k2

  • X1/x2 = k2/k1

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


  • 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 sprainDislocated shoulderTibialis Posterior tendon problems

  • 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

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


Hydrostatic pressure

  • 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


  • 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

Hydrodynamic principals of Hydrotherapy

  • Characteristics of water

    Mass, weight, density, specific gravity, buoyancy, hydrostatic pressure, surface tension


    Any mvt creates turbulance it can assist as well as resist mvt

  • Laminar flow

  • Turbulent flow

  • 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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