bulk properties of solids Flashcards
breaking stress/ ultimate tensile stress
minimum tensile stress required to break a material
brittle
a brittle material will not deform plastically
brittle fracture
tiny cracks go through the material until they get bigger and it breaks
crumple zone
deforms plastically transform kinetic energy into heat energy and then elastic potential energy which can return to kinetic energy the more kinetic energy that is converted back will increase the force exerted on the people as their velocity’s change by a greater amount
density
mass per unit volume ( p the Greek letter “rho”)
elastic behaviour
a sample of material behaves elastic if when the deforming force is removed it returns to its original shape
elastic limit
the force or stress which is exceeded causing permanent deformation
elastic potential energy
the energy stored in a material when its stretched
uncertainty
the range in which the answer should lie
factional uncertainty
the uncertainty show as a fraction of the value
how do you combine uncertainties
the uncertainties have t o be in percentage form and then you always add
hooks law
the extension of a material is directly proportional to the force applied this applies to all materials that follow hooks law and haven’t passed their elastic limit
limit of proportionality
the maximum force or extension that can happen and the material still have extension directly proportional to the force
plastic behaviour
a material behaves plastically when even when the force is removed it remains with some deformation
tensile strain
change in length over original length
tensile stress
force over cross sectional area
ultimate tensile stress
the maximum force a material can withstand not always the same as the breaking stress which is when the material breaks
stiffness constant
the k in F=k/\L it is the force per unit extension required to extend a material
yield point
the point or stress at which a material becomes less stiff and gives a greater extension per unit force
Younge modulus
ration of tensile stress over tensile strain for a material before there elastic limit. the young’s modulus depends on the properties of the material only not the size or shape of the material
why do we often use a graph to figure out the young’s modulus
because it uses a line of best fit which reduces the random errors
give one positive and one negative for using a thin wire of material to find the young’s modulus
pro- it means there will be a greater extension per unit force meaning there will be a smaller percentage uncertainty in the measurement for the extension
con- there will be a greater percentage uncertainty for a smaller diameter affecting the cross sectional area
what do micrometres measure too
0.01mm
at do vernier calliper measure too
0.1mm
what is the space between unloading and loading measurements on a force extension graph of a material that has not gone past its elastic limit
it is called the hysterias is it caused because when the material is stretched work is done on the a material and so energy is transferred which get dispersed as heat energy
what is the area under a force extension graphs
the area underneath is equal to the work done and so equal to the elastic potential energy
