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Physics The Good One > 04 Materials > Flashcards

04 Materials Flashcards

1
Q

What is density?

A

Density = mass / volume

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2
Q

What is Archimedes’ principle?

A

Upthrust = weight of fluid displaced

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3
Q

What is a fluid?

A

A substance that can flow

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4
Q

What is density?

A

A measure of the mass per unit volume of a substance

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5
Q

What is upthrust?

A

An upwards force on an object caused by the object displacing fluid

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6
Q

What is a hydrometer?

A

An instrument used to determine the density of a fluid

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7
Q

When is viscous drag exerted?

A

When an object is in laminar flow

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8
Q

What does viscous drag depend on?

A

Viscosity of fluid, speed of body, surface area

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9
Q

What is mass?

A

The amount of matter in an object

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10
Q

What is viscous drag?

A

A resistive force acting on an object traveling through a fluid

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11
Q

What is Stokes’ law?

A

F = 6πrηv

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12
Q

What are the units of the coefficient of viscosity

A

η? Nm^-2s or Pas

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13
Q

What does Stokes’ law apply to?

A

Small spherical objects traveling at slow speeds with laminar flow

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14
Q

What are the steps in proving the viscosity equation?

A
  1. Sum of forces W = U + F
  2. W = m(s)g, U = m(f)g, F = 6πrηv
  3. m = ρV
  4. V = 4/3πr³
  5. Cancel like terms in each expression
  6. Rearrange for η
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15
Q

What are some uses for Stokes’ law?

A

Alcohol testing, food, sports, car design, medicine, cosmetics

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16
Q

How do you measure the volume of irregular objects?

A

Measure how much water it displaces

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17
Q

What is upthrust?

A

Weight of fluid displaced

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18
Q

What are the properties of laminar flow?

A

Streamlines, no mixing of layers

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19
Q

What are the properties of turbulent flow?

A

Dissipation of energy, eddy currents, mixing of layers

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20
Q

What forces act when a material is stretched?

A

The stretching force, interatomic forces

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21
Q

What is Hooke’s law?

A

The force is directly proportional to the extension (and compression)
F = kx

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22
Q

What is the gradient of a force-extension graph?

A

The stiffness (spring constant) (nm^-1)

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23
Q

What is the limit of proportionality on a force-extension graph?

A

Where the gradient stops being constant

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24
Q

What is the yield point on a force-extension graph?

A

Where the gradient levels out (no longer proportional)

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25
Q

What is the elastic limit on a force-extension graph?

A

Between the limit of proportionality and yield point

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26
Q

What is the breaking point on a force-extension graph?

A

when there is a fracture

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27
Q

What is elastic deformation?

A

Material returns to its original shape once the deforming force has been removed

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28
Q

What is plastic deformation?

A

Material does not return to its original shape once the deforming force has been removed

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29
Q

What is the yield point?

A

Where there is a large increase in extension for a small increase in force

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30
Q

What does the steeper the gradient of a force-extension graph mean?

A

The stiffer the object

31
Q

What is elastic potential energy?

A

The work done to stretch a spring

32
Q

How do you calculate elastic potential energy from a force-extension graph?

A

Area underneath the graph (up to the limit of proportionality)

33
Q

What is the formula for elastic potential energy?

A

Elastic potential energy = 1/2Fx

34
Q

What are the properties of materials?

A

Stiff/flexible,
elastic/plastic,
ductile/malleable,
tough/brittle

35
Q

What is flexible?

A

Small force for large extension

36
Q

What is ductile?

A

Can be drawn into wires, materials that can be stretched or bent without breaking under stress

37
Q

What is malleable?

A

Can be hammered into shape

38
Q

What is tough?

A

The ability to absorb energy and plastically deform without fracture

39
Q

What is brittle?

A

materials that are easily broken, cracked, or snapped when subjected to stress. Brittle materials have little or no plastic deformation

40
Q

How does area affect how much a wire stretches?

A

Thin wires stretch more
, thick wires stretch less

41
Q

What is tensile stress?

A

Tensile stress = force/area

42
Q

What is the unit of stress?

A

Pascal

43
Q

What is the difference between stress and pressure?

A

Stress only happens to solids, pressure applies to a surface stress occurs throughout the solid

44
Q

What is ultimate tensile stress?

A

The maximum stress reached before fracture

45
Q

What is tensile strain?

A

Tensile strain = extension / original length

46
Q

What is the unit of strain?

A

No unit (it’s a ratio/fraction)

47
Q

What is Young’s modulus?

A

Young’s modulus = stress/strain

48
Q

What is Young’s modulus? definition

A

A property of a material that measures how difficult it is to change the shape of a material

49
Q

What is the unit of Young’s modulus?

A

Pascals

50
Q

How do you find Young’s modulus in an experiment?

A
  1. Measure the diameter of the wire
    2.measure the original length of the wire
    3.attach the wire to the desk and thread it over a pulley with hanging masses on the end
    4.put a sticky label on the wire at the end of the meter ruler
    5.add the masses to the hanger and record the distance movement of the sticky marker
  2. workout area through pi x r^2
  3. workout stress for each value through force / area
  4. workout strain through the extention /original length
  5. plot stress x strain
  6. gradient is young
51
Q

What is the area under a stress-strain graph?

A

The energy stored per unit volume

52
Q

What is hard?

A

Resistant to indentation or surface is resistant to plastic deformation

53
Q

What is stiff?

A

Large force for small extension

54
Q

What is high tensile strength?

A

Undergo a large stress/force before breaking

55
Q

What is a linear relationship?

A

Increase in x is constant for fixed increases in y

56
Q

What happens when a wire passes its limit of proportionality?

A

There is a large increase in extension for a small increase in mass.
It will no longer return to its original shape as it has been plastically deformed.

57
Q

How can you make the extension measurement more accurate?

A

Use a pointer on the wire/masses to make it easier to read,
read at eye level to avoid parallax, use a set square to ensure the ruler’s vertical,
wait for extension to finish,
add masses gently

58
Q

What is laminar flow?

A

Where the layers of flow are parallel and do not mix/cross, no abrupt change in speed or direction of flow.

59
Q

What is turbulent flow?

A

Where the layers of flow mix forming eddy currents and causing energy to be dissipated. Random changes in speed or direction.

60
Q

What is F in Stokes’ law?

A

Viscous drag

61
Q

What happens when spring constants are in parallel?

A

Kt = K1 + K2

62
Q

What happens when spring constants are in series?

A

1/Kt = 1/K1 + 1/K2

63
Q

What is the viscosity equation?

A

(2gr²(ρs - ρf))/9v = viscocity

64
Q

How do you find the drag on an object?

A

Drag = ± upthrust ± weight (measure radius + mass of object & use known densities)

65
Q

What is the area under a stress-strain graph?

A

Toughness (energy it can absorb before it snaps)

66
Q

What is the difference between compressive strain and tensile strain?

A

Compression decreases in length, tensile increases in length

67
Q

Accuracy

A

how close you are to the true value

68
Q

sensitivity

A

how small a division a piece of equipment can measure to

69
Q

precision

A

how similar repeated values are

70
Q

whats the relationship between upthrust and weight when the object is floating with no movement

A

Upthrust of fluid = weight of object
pfvfg=povog
pfvf=movo

71
Q

whats the relationship between upthrust and weight when the object is floating on the surface but is partiall submerged

A

density of fluid > density of object
Uf =Wo

72
Q

if the object is fully submerged

A

volume is the same therefore the densities of the submerged object and material around is the same.
pf=po

73
Q

free body diagram of falling

A

^ Force due to drag
I
I Upthrust+Drag=weight
O
I ^
I I upthrust
I
v Weight

74
Q

free body diagram of rising

A

^ upthrust
I
I
I Upthrust=Drag+weight
O
I I Drag
I v
v Weight

Physics The Good One (16 decks)

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