Materials Flashcards
Elastic limit
The point when the material stops behaving elastically and starts behaving plastically so it does not return to its original length when the force causing deformation is removed
Yield point
When the material suddenly starts to stretch without any extra load (large increase stress, for a small increase strain)
Elastic deformation
When a material being stretched would return to its original length when the force causing deformation had been removed.
Plastic Deformation
When a material being stretched has permanently been deformed and will not go back to its original length
Breaking stress
The point at which the material breaks
The limit of proportionality
The point beyond which Hooke’s law no longer applies when stretching a material (the point where the graph curves)
Laminar flow
Where all the parts of the fluid are flowing in the same direction and the layers in the fluid do not mix
Turbulent flow
A flow pattern where all the parts of the fluid get mixed up
Upthrust
An upward force that fluids exert on objects that are completely or partially submerged in a fluid
Viscous drag
The friction between the surface of the object and the fluid when an object moves through a fluid, or when a fluid moved past an object
What is Upthrust caused by?
Caused because the top and the bottom of the object are at different depths. Since P = h x density x g, there is a difference in pressure which causes an overall upwards force known as upthrust
Explain why Upthrust = weight of fluid displaced
F = pA = h1(from top of object to surface of water) x density x gravity
F = pA = h2(from bottom of object to surface of water) x density x gravity
Net force = (h2-h1) x density x gravity x Area
= Volume x density x gravity
= mass x gravity
= weight (of displaced fluid)
Stokes law
Viscous drag, F = 6 pi x eta x r x v
What is viscosity dependent on?
Temperature
(Increase temp, decrease viscosity in liquids)
(Increase temp, increase viscosity in gases)
What does stokes law apply to?
Small spherical objects moving at low speeds with laminar flow
