ch 7 - matter and materials Flashcards
density definition
mass per unit volume
. symbol = /p/ (rho)
. units = kg m¯³, g cm¯³
density formula
p = m/v
1000 kg m-3 =
1 g cm-3
density of water ≈
1000 kg m-3
what is pressure
the normal/perpendicular force acting per unit cross sectional area
what is pressure
the normal/perpendicular force acting per unit cross sectional area
. symbol = p
. units = Pa = Nm-2
pressure formula (solid)
p = F/ A
pressure formula (fluid)
<>p = pgh
p = <>p + P atm
change in pressure in fluids formula derivation
vol = Ah
mass of water = p * Ah
weight of water = pAhg
change in pressure = F/A
change in pressure = pAh*g/A
change in pressure = pgh
what is Archimedes’ principle
the upthrust on a body is equal to the weight of the fluid that displaces it
upthrust formula
phV
upthrust formula derivation
= F2 - F1
= pg(h2 - h1) A
= pghA
= pgV
compressive forces
describes a force that squeezes and shortens an object
what are tensile forces
associates with tension or pulling
what is extension
the increase in the length of a material from its original length
hooke’s law
force is proportional to extension until the limit of proportionality/ elastic limits
spring constant
the force per unit extension for a spring, unit = Nm-1
k = F/x
the limit of proportionality
the point beyond which extension is no longer proportional to the force
what is elastic deformation
an object that returns ti its initial length when the force is removed has deformed elastically
what is platic deformation
an object that does not return to its initial length when the force is removed is deformed permanently
what is an elastic limit
the value of stress beyond which an object will not return to its original dimentions
what is strain
extension / length
symbol : curved E
unit : none
what is stress?
force per unit cross sectional area that acts at right angles to a surface
F/A
unit : Pa
symbol : sigma
what is Young modulus?
the stress in material divided by the strain
E = stress / strain
gradient
high young modulus, high stiffness
what is elastic potential energy / strain energy
energy stored in a body due to a chnage in its shape
elastic potential energy formula derivation
work done
final force/2 * extension
0.5Fx
OR
area = 0.5 bh
0.5Fx
elastic potential energy formula
E = 0.5Fx = 0.5 kx²
area under a force extension graph
work done by force
