Materials Flashcards
What is Archamedes principle?
The up thrust is equal in magnitude to the weight of fluid displaced by the body
How does an object float?
If it can displace its own weight of fluid without submerging
Describe laminar flow
Lower speeds, more streamlined objects, flow in layers, layers don’t mix except on a molecular level, parallel, no sudden changes in speed or direction
Describe turbulent flow
Flow is chaotic. subject to sudden changes in speed and direction, large scale mixing of layers, lots of EDDIES
Describe viscosity
Fluids with lower viscosity will have a greater rate of flow and cause less viscous drag, measured in kg m^-1 s^-1 and Pas.
It decreases with temperature ; Increases with temperature in gases and its unit is Nsm-2
When does something obey Hooke’s Law?
When it is a straight line through origin we can say that it is directionally proportional and obeys on a force extension graph
Definition of brittle and example
Material breaks with little or no plastic deformation. Glass
Definition of malleable and example
Material can be beaten into sheets; shows a large plastic deformation. Gold
Definition of stiff and example
Very small deformation when endures large forces. Steel bar.
Definition of ductile and example
Can be pulled into wires/ threads, shows plastic deformation before failure under tension. Copper wire
Definition of hard and example
Resists plastic deformation by surface indentation or scratching. Diamond
Definition of tough and example
Can withstand impact forces and absorb a lot of energy before breaking; large force produces moderate deformation. Car tyres
How do you calculate elastic strain energy?
Area under a force/extension graph
How do you calculate young modulus?
Gradient of a stress/strain graph gives Young Modulus as well as stress divided by strain and units are Nm-2 or Pa
Describe tensile strength
When a material is being stretched
