Topic 6: deformation of solids Flashcards
state Hooke’s law
for a material that obeys Hooke’s law, its extension is directly proportional to the force exerted on it up to the limit of proportionality.
when does an object reach its elastic limit
right after the limit of proportionality
what is elastic deformation
before elastic limit, the object will return to its original shape after a load is removed.
what is plastic deformation
after elastic limit, the object will not return to its original shape after a load is removed.
what is the equation for spring constant
spring constant = force ÷ extension
what are the units for spring costant
Nm^-1
what is the equation for elastic energy (and work done) including force
W = Ep = ½Fx
What is the derived equation from W = Ep = ½Fx
W = Ep = ½kx^2
how do you find the work done from a force-extension graph
the area under the graph
what is the spring constant of 2 springs in series
k = F ÷ 2x
what is the spring constant of 2 springs in parallel
k = 2F ÷ x
define stress
force per unit area (cross-sectional area)
what is the equation for stress
stress = force ÷ area
what are the units for stress
Nm^-2 or Pa
what is the symbol for stress
sigma, σ
what is tensile stress
a stretch
what is compressive stress
a squash
define strain
extension (or compression) per unit length
what is the equation for strain
strain = extension ÷ original length
what is the symbol for strain
ε
define young modulus
the ratio of stress and strain
explain young modulus
how stiff a material is, the measure of the ability of a material to withstand changes in length with an added load.
what is the word equation for young modulus
young modulus = stress ÷ strain
what is the symbol equation for young modulus
E = FL ÷ Ax
What is the symbol for young modulus
E
What are the units for young modulus
Nm^-2
what can you interpret from a force extension graph within the elastic limit
the elastic potential energy is the area under the graph
