Topic 4:Materials Flashcards
What is the equation for Density
P=M/V
Define turbulent flow
where all parts of the fluid cross over into each other and don’t move in a parallel direction.
Define laminar flow
Where all the parts of a fluid are flowing in the same direction(parallel direction)
what are the features of Turbulent flow
Layers cross over
Produces swirls and eddies
Chaotic movement
Happens at high speeds
Non uniform
What are the features of Laminar flow
Parallel Layers
Occurs at lower speeds
Streamline
Velocity is constant over time
uniform
What does turbulent flow cause
Drag
What is upthrust equal to
Weight of the fluid displaced
Define viscosity
The measure of how resistant a fluid is to flowing
What happens to viscosity when heat increases
When heat of a liquid increases viscosity decreases
What happens to velocity when viscosity increases
The higher the viscosity the more slowly a liquid flows
+viscosity = - velocity
Define drag
The forces that oppose the motion of an object moving through a fluid (gas or liquid)
What is the equation for stokes law
F=6πrηV
Derive the equation for terminal velocity on a spherical object falling downwards
weight =upthrust +Drag
P=M/V so M=P x V
W=MxG
so W=P x V x G
W=Ps x 4/3πr^3 x G
Upthrust= weight of fluid displaced
Weight of fluid displaced = volume of object
V=4/3πr^3
U=4/3πr^3
W=U so
U= Pf x 4/3πr^3 x G
stokes law 6πrηV
W=U+D(stokes law)
Ps x 4/3πr^3 x G = Pf x 4/3πr^3 x G + 6πrηV
(Cancel πr)
(- Pf x 4/3r^2)
then collect like terms
4/3r^2g(Ps–Pf)=6ηV
V=4/3r^2g(Ps–Pf)/6η
V=2/9r^2g(Ps–Pf)/η
Which way does drag act on a falling object
upwards
what is the volume of a sphere
4/3πr^3
which way does drag act on a rising object
downwards
Define Hooke’s law
The force applied to a spring is directly proportional to its extension
what is weight equal to as a spherical object falls through a liquid at a terminal velocity an the forces are balanced
Weight=upthrust+stokes law
What is the equation for Hooke’s law
F=KE
Define Elastic deformation
When an object can compressed/Stretched and returns back to its original shape
Define Inelastic deformation
When an object can compressed/Stretched but doesn’t return back to its original shape
What is the Equation for elastic potential energy
EPE=1/2K x X^2
How do you find energy from a Force/Extension graph
Finding the area under the graph using the equation
1/2 FxE
What is the gradient of a force extension graph
Spring constant
Define spring constant
Stiffness(how easy or hard it is to stretch)
In a force extension graph define the
Elastic Plastic and fracture stages
Elastic= the point where the object will deform and return to its original shape
Plastic= the point where the object will continue deforming with added force, not returning back to its original shape
Fracture=The point where the object breaks
Define stress
Force per unit of a cross sectional area
Define strain
Extension per unit length
What is the equation for Stress
σ=Force/Area
What is the equation for Strain
ε=Extension/Length
What is young modulus
The ratio between stress and strain
what is the Equation for young modulus
Stress/ Strain
Force/area
_____________
Extension/length
Force x length
___________
Area x extension
Whats another way to write young modulus
Fx/AΔx
What is the unit for young modulus
Nm^-2
What is the gradient of a stress strain graph
Young modulus
What is the Elastic limit
beyond this, the material is permanently deformed & wont return to its original shape
What is the limit of proportionality
From this region onwards the metal can still behave elastically but cannot be relied upon to do so
What is Yield point
Beyond this point material undergoes a sudden increase in extension(as the atoms reorganise themselves significantly)
What is the Breaking/fracture stress
The stress Which causes the material to break.
What is the ultimate Tensile Stress
The highest value of stress the material can ever attain
Define stokes law
A way to calculate viscous drag
Define viscous drag
Viscous drag is The friction between the surface of a object and a fluid as it the object moves through the fluid
what is the equation for work done
W=force x displacement/distance
