Materials Flashcards
What is density ?
Mass per unit of volume.
What is the formula for density ?
ρ = M/V
What will happen if the density of an object is greater than a liquid ?
it will sink.
How do you find density of a regular solid ?
Measure mass with a balance
Calculate volume by measuring dimension
How do you find the density of a liquid ?
Measure mass of container
Measure mass of container with liquid in it
Calculate mass of liquid
Read volume of liquid off container.
How do you find the density of a irregular shape ?
Measure mass using balance
Place object in a container with known volume of liquid and calculate change in volume.
What is Hooke’s law ?
The force applied to a wire or spring in directly proportional to extension up until the limit of proportionality.
What is the equation for Hooke’s law ?
F = KΔL
What is the gradient of a force extension graph ?
spring constant.
What is the elastic limit ?
Point of which the spring or wire will not return to its original size.
What is the fracture point ?
Point at which the spring or wire breaks.
What is strain energy ?
Work done in stretching a wire or spring.
What is the area under a force extension graph ?
Strain energy/ work done.
What is the formula for strain energy ?
E = 1/2 K ΔL
What is plastic deformation ?
Where an object is stretched beyond its elastic limit and will not return to original size/shape
What makes something ductile ?
Large plastic region.
What makes something brittle ?
Very small plastic region.
What is the area between the loading and unloading curve ?
Work done in causing permanent deformation / energy transferred to thermal.
Why is rubber a unique material ?
Its stiffness is always changing
doesn’t get plastically deformed.
area between loading and unloading curves is wasted energy converted into thermal energy.
What is stress ?
Tension per unit of cross sectional area. (Pa / Nm^-2)
What is strain ?
Extension per unit of original length.
What is the formula for stress ?
F/A
What is the formula for strain ?
ΔL / L
What is Young modulus ?
Energy required double a materials length (Pa)
What is the formula for Young Modulus ?
FL / Ae
or
stress/strain
What is the gradient before the limit of proportionality on a stress strain graph ?
Young Modulus.
