unit 1 materials

Question 1

Density

Answer 1

Mass per unit volume
ρ = m/V

Question 2

Upthrust

Answer 2

due to different pressure exerted on surface of object

Question 3

Archimedes law

Answer 3

upthrust = weight off displaced volume
= ρVg

Question 4

Stokes Law

Answer 4

F = 6πηrv

viscous drag force under assumption: small, spherical, laminar, slow

Question 5

laminar flow

Answer 5

smooth paths, little to no mixing between adjacent layers of fluid

Question 6

turbulent

Answer 6

mixing between layers and form separate currents

Question 7

viscosity

Answer 7

how resistant a fluid is to deformation

determined by internal frictional forces

Question 8

relationship of viscosity and temp

Answer 8

η is temperature dependent

-liquids: T ↑ η ↓

-gases: T ↑ η ↑

Question 9

hookes law

Answer 9

Extension is directly proportional to force until the spring reaches it’s elastic limit

-ΔF = kΔx

(F: external force, k: stiffness(spring constant), Δx: extension)

Question 10

stress

Answer 10

force per unit cross sectional area

unit: Pa (N/m²)

Question 11

strain

Answer 11

change in length over original length

unit: dimensionless

Question 12

Young Modulus

Answer 12

value that describes stiffness of material (ratio of stress applied and resulting deformation)

-E=σ/ε=(F/A)/(Δx/L)

Question 13

Limit of proportionality

Answer 13

The limit beyond which, when a wire or spring is stretched, its extension is no longer proportional to the force that stretches it.

Question 14

Elastic limit

Answer 14

Maximum stress that a material will withstand without plastic deformation.

Question 15

yield point

Answer 15

point where materials begins to rapidly extend without additional stress.

Question 16

elastic deformation

Answer 16

material returns to original shape once applied force is removed
all work is stored as elastic strain energy

Question 17

plastic deformation

Answer 17

materials shape is changed permanently
some work is also dissipated as heat

Question 18

elastic strain energy

Answer 18

area under: force-extension graph
ΔE = 0.5kΔx² = 0.5FΔx
unit: J

Question 19

ductile

Answer 19

can undergo large plastic deformation before breaking/
look for: max x value

Question 20

brittle (brittleness)

Answer 20

extend very little: likely to fracture at low strain
look for: min x value

Question 21

strong (strength)

Answer 21

requires large force/stress to break
look for: max y (high UTS)

Question 22

tough (toughness)

Answer 22

can withstand repeated deformation
look for: max area under curve

Question 23

elastic (elasticity)

Answer 23

non-permanent deformation, bonds are stretched but not torn apart

Question 24

stiff (stiffness)

Answer 24

how resistant a material is to elastic deformation (Young modulus)
look for: slope (linear)

Question 25

hard

Answer 25

doesn’t scratch easily

Question 26

durable

Answer 26

can be repeatedly loaded/unloaded without change in properties