Materials Fluids and Fluid Flow 1 Fluids and Fluid Flow 2 Force and Extension Stress, Strain, and...
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Transcript of Materials Fluids and Fluid Flow 1 Fluids and Fluid Flow 2 Force and Extension Stress, Strain, and...
![Page 1: Materials Fluids and Fluid Flow 1 Fluids and Fluid Flow 2 Force and Extension Stress, Strain, and the Young Modulus.](https://reader035.fdocuments.net/reader035/viewer/2022062222/56649ca85503460f9496ad64/html5/thumbnails/1.jpg)
Materials
• Fluids and Fluid Flow 1• Fluids and Fluid Flow 2• Force and Extension• Stress, Strain, and the Young Modulus
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Turbulent + Laminar Flow• Laminar /Streamline Flow– layers do not cross
each others paths. Occurs at lower speeds.• Turbulent Flow – layers cross and mix. Occurs at
higher speeds.
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Viscous Drag Force• The force of friction caused by a flowing fluid• Is in the opposite direction to movement
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Upthrust Force• Upthrust is a force that acts vertically upwards
on an object in a fluid• Upthrust = weight of fluid displaced
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Density• A measure of how close-packed the particles
are in a substance. EG: gases are much less dense than solids and liquids because their particles are more widespread.
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Terminal Velocity• As an object falls it’s speed increases. The
drag on it will also increase. Eventually a speed is reached where the drag force = the weight. As there is no net force on the object, the acceleration will be zero.
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Viscosity• The higher the viscosity of a fluid, the slower it flows.• Viscosities of most fluids decrease as the temperature
increases. Fluids generally flow faster if they are hotter.
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Stokes’ Law• Calculates the drag force on a sphere as it
travels through a fluid.• F = viscous drag force acting on the sphere• r = radius of the sphere• n = viscosity of the fluid• v = velocity of sphere
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ALL Forces on a Falling SphereStokes’ Law + Upthrust = Weight
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Hooke’s Law• The extension of a sample of material is directly
proportional to the force applied.• Hooke’s Law does not apply to all materials• k = stiffness = the gradient = F/x
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Force v Extension/Compression Graphs• Limit of Proportionality – The point beyond
which force is no longer directly proportional to extension (line is no longer straight)
• Elastic Limit – This is when the force is taken away, the material no longer goes back to its original length
• Yield Point – Material shows a greater increase in extension for a given increase in force
• Ultimate Tensile Stress – The maximum stress that the material can withstand
• Breaking Stress – the point at which the material breaks
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• Ultimate Tensile Strength: the maximum stress (force) a material can withstand.
• Breaking Stress: the stress at which the material breaks. Can be the same as UTS.
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Stress and Strain•Stress (N/m2)
= Force (N) / Area (m2)
•Strain (no units)
= Extension (m) / Original Length (m)
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Young ModulusYM = Stress/StrainYM = (F/A)/(E/L)
YM = FL/EA• YM = the gradient of a stress/strain graph• The greater the YM (the steeper the gradient)
the stiffer the material. Ie: the less it stretches for a given force.
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Elastic and Plastic Deformation• At point A, Masses (Force) are unloaded from the
material. • Plastic deformation has occurred as the material
has not gone back to it’s original length.
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Material Characteristics1. Brittle: Breaks suddenly without deforming plastically.
Follows Hooke’s Law until it snaps. Glass.2. Ductile: Undergos plastic deformation by being pulled
into wire. Retains strength. Copper.3. Malleable: Undergos plastic deformation by being
hammered or rolled into shape. Loses strength. Gold. 4. Hard: Resist plastic deformation by compression or
scratching rather than stretching. Diamond.5. Stiff: Measure of how much a material stretches for a
given force. Bamboo.6. Tough: Measure of the amount of energy a material
can absorb before it breaks. Toffee.
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Elastic Strain Energy• Plastically deformed material:– E = ½ x Force x Extension (Similar to W=Fs)
• Elastically deformed material:– E = area under force/extension graph