Section 4 Flashcards
When will a material deform
When there’s a pair of opposite forces acting on it
Hooke’s law
The extension of a wire is proportional to the force applied, assuming the elastic limit has not been exceeded
k
force constant
Nm-1
elastic limit
When the wire no longer follows hookes law and is permanently stretched
in series
half as stiff
in parallel
double k
Elastic deformation
When put under tension the atoms are pulled away from each other
The atoms can move slightly relative to their equilibrium position, without changing position and return back when the load is removed
plastic deformation
the atoms move position relative to one another and do not return to their original postions
tensile stress
force applied / cross sectional area
tensile strain
extension / original length
the greater the force the greater the __________?
stress
breaking stress
when the atoms separate completely and the material breaks
area under force/extension graph
elastic potential energy
how to work out elastic potential energy
E = 0.5 Fx E = 0.5 k x^2
Youngs modulus
stress/strain
strain units
doesn’t have units
its a ratio
finding youngs modulus graph
gradient
area under graph is epe
yield point
the stress at which a large amount of plastic deformation takes place with a constant or reduced load
Ductile material
Hookes law
limit of proportionality
elastic limit
yield point
brittle material
no plastic deformation
brittle fracture
polyethene
behaves plastically
ductile
rubber
elastically
heat energy is given inbetween the curves
