11 Materials Flashcards
density of a substance
mass per unit volume of the substance
D=m/v
hooke’s law
the extension of a spring is proportional to the force needed to extend it
F=k∆L
(k= spring constant and stiffness )
elastic limit
point beyond which a wire is permanently stretched
elasticity
property of a solid that enables it to regain its shape after it has been deformed or distorted
pascal
unit of pressure or tree equal to 1Nm-1
stress
force per unit area of cross-section in a solid perpendicular to the cross-section
T/A
strain
extension per unit length of solid when deformed
∆L/L
young modulus
stress/ strain (assuming the limit of proportionality has not been exceeded)
TL / A ∆L
yield point
ponit at which the tree in a wire suddenly drops when the wire is subjected to increasing strain
elastic limit
point beyond which a wire is permanently stretched
plastic deformation
deformation of a solid beyond its elastic limit
ultimate tensile stress
tensile stress needed to break a solid material
breaking stress
tensile stress needed to break a solid material
brittle
snaps without stretching or bending subject to stress
ductile
stretches easily without breaking
limit of proportionality
the military beyond which, when a wire or a spring is stretched, its extension is no longer proportional to force that stretches it
measure the density of a solid
- measure mass
- calculate dimension and then the volume (sphere radius = 4/3 π r^3)
measure the density of a liquid
- measure mass
- measure the volume in measuring cylinder
measure the density of a irregular solid
- measure the mass
- measure the amount of water it displaces
- D=m/v
density of alloys
add the two density together
springs in parallel
spring constant
K= Kp + Kq
springs in series
spring constant
1/K = 1/Kp + 1/Kq
energy stored in a stretched spring
Ep=1/2 F∆L = 1/2 K∆L^2
elastic energy stores in a stretched wire
1/2 T ∆L
area under force - extension graph
Elastic strain energy
Up to the elastic limit of a sample, all the work done in stretching it is stored potential energy, or Elastic Strain Energy
