Chapter 6: materials Flashcards
define tensile force
force that produces an extension
define compressive force
force that produces a compression
define elastic limit
the point after which an object becomes permanently deformed
define elastic
material that allows the object to return to its original shape and size after a force has acted on it
define plastic
material that causes an object to become permanently deformed after a force has acted on it
what is the force/spring constant equation
F = k e/x Force = spring constant x extension
what is the equation for working out the spring constant for springs in parallel
K1 + K2 + K.. = Kt
spring constant 1 + spring constant 2 + etc = total spring constant
what is the equation for working out the spring constant for springs in series
1/K1 + 1/K2 + etc = 1/Kt
1/spring constant 1 + 1/spring constant 2 + etc = 1/total spring constant
describe what the force/extension graph would look like for a strong object
a strong object would have a steep gradient then a curve then it would stop
describe what the force/extension graph would look like for a polymer
a polymer has a curve that looks like a cubic graph before snapping or having a linear return whilst being permanently deformed
what happens the closer you get to the elastic limit
it becomes harder to stretch an object
what is the elastic potential energy equation
EPE = 0.5 k e^2
elastic potential energy = 0.5 x spring constant x extension squared
what is the gravitational energy equation
GPE = m g h
Gravitational potential energy = mass x gravitational field strength x height
what is stress
measure of force compared to the area acted upon
what is the stress equation
σ = F/A stress = force/area
what are the units for stress
Pa Pascals
Nm^-2 Newtons per metre squared
what quantity is stress
vector because it has direction and magnitude
what is strain
strain is a ratio that is a measure of extent of deformation
what is the linear strain equation
Ɛ = x/L or e/L
linear strain = extension/length
what are the three forms of strain and what do they mean
elastic (object returns to original shape and size)
plastic/ductile (object is permanently deformed)
brittle (object will snap)
what is Young’s Modulus
measure of the stiffness of an object
what is the Young’s Modulus equation
E = σ/Ɛ
Youngs Modulus = stress/strain
