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

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 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)

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

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 & bandThe 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

HYDROTHERAPY

HYDROSTATIC PRESSURE

o 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

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

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

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