What is Hooke's Law?
F=kx
k=Fx
The extension of an elastic body is proportional to the force that causes it (within its elastic limit)
The force on a body is proportional to the extension caused once past the elastic limit
Force is proportional to strain
In Hooke's law, what is k?
The spring constant
Extension
The length
How do you find the spring constant from a Force- extension graph?
1 ----------- gradient
gradient
area underneath
What does the area underneath a force-extension graph tell you?
The strain energy
The strain
The stress
Nothing
What is strain energy?
Energy stored in deformed materials
Work done in producing an extension
The maximum force a material can take before breaking
The point at which a material reaches its elastic limit
Ultimate tensile strength is...
the maximum tensile force that can be applied to a material before it breaks
the energy stored in a material when it's stretched to its limit
the maximum stress of a material
tensile force is a force applied to create a stretch
Stress =
force/area
force x area
force applied per unit cross sectional area
measured in Pa
measured in Nm^-2
the fractional change in length under load
Fractional change in length under load =
Stress
Strain
Young modulus
Strain energy
Strain is measured in N/m
extension/length =
stress
strain
young modulus
What's the effective spring constant of springs in parallel?
k1 + k2
1/K1 + 1/K2
k1 x k2
Which is in parallel and which is in series (top or bottom)?
top - series bottom - parallel
top - parallel bottom - series
How do you find the effective spring constant of two springs in series?
1/K = 1/k1 + 1/k2
1/k = k1 x k2
k = k1 + k2
What is a ductile material?
materials that have a large plastic region and can therefore be drawn into wires
Materials that have a very small elastic limit and therefore break easily
Materials that are very stretchy
Brittle materials distort very little and fracture beyond their elastic limit
What material is this a graph showing?
brittle material
ductile material
elastic material
polymeric material
What's the equation for strain energy?
E=1/2Fx
E=1/2kx^2
E=1/kx
E=kFx/2
What is the young modulus?
A constant for a given material
Stress/strain
Fl/Ax
the stiffness of a material
The maximum force a material can withstand before fracturing
A material with a small young modulus is stiff
On a stress-strain graph what is the yield point?
The point from which the force required to stretch a material decreases
The point from which the force required to stretch a material increases
The elastic limit
On a stress-strain graph what is the limit of proportionality?
The elastic limit, above which plastic deformation occurs
The elastic limit, above which elastic deformation occurs
The maximum force applied to a material before it breaks
The point at which a material fractures
Plastic deformation is reversible and disappears when the load is removed
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