Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A Level Physics Year 1 > Materials > Flashcards

Materials Flashcards

You may prefer our related Brainscape-certified flashcards:
Physics 101 flashcards AP® Physics flashcards
1
Q

What is the density of a material?

A

Its mass per unit volume

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the equation for density?

A

Density = mass / volume

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What 1 g cm^-3 equal to?

A

1000 kg m^-3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Why does oil float on water?

A

It has a lower density than water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Why will a solid object float on a fluid?

A

If its density is less than the density of the fluid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is Hooke’s Law?

A

The extension of a stretched wire is directly proportional to the force applied

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What happens, in terms of forces, when a light metal wire is supported at the top and then has a weight attached at the bottom?

A

The weight pulls down with a force, stretching the wire. Once the wire stops stretching, the forces will be in equilibrium and there will be an equal and opposite reaction force at the support

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is an objects stiffness constant?

A

The force needed to extend it by 1m

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the equation for Hooke’s Law?

A

Force = stiffness constant x extension

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does a tensile force do?

A

Stretches something

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does a compressive force do?

A

Squashes something

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are 2 features of a force-extension graph that shows the material obeys Hooke’s Law?

A

It’s a straight line through the origin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the gradient of a force-extension graph equal to?

A

Stiffness constant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

At what point on a force-extension graph does an object reach its elastic limit?

A

When the graph starts to curve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What happens if you increase the force past the elastic limit?

A

The material will be permanently stretched (and won’t go back to original shape when force is removed)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the elastic limit of an object?

A

The force beyond which a material will be permanently stretched

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the limit of proportionality?

A

The point beyond which the force is no longer proportional to the extension (so the gradient of a force-extension graph is no longer linear)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

On a force-extension graph, where do you mark the limit of proportionality?

A

When the line of the graph is no longer straight

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are 5 the steps for the experiment to investigate the extension?

A
  • Set up a clamp stand and clamp with a spring attached
  • Take a measurement of the original length of the spring
  • One at a time, add weights to the bottom of the spring, and measure the new length
  • Calculate extension by doing extension = new length - original length
  • Plot a graph of force against extension
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

When investigating the extension of a spring in a lab, why do you trial investigation first?

A

So you can work out the size and range of weights to get lots of measurements before the objects break

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What does loading mean?

A

Increasing the force on the material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What does unloading mean?

A

Reducing the force on the material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is elastic deformation?

A

Where the material returns to it’s original shape once the forces are removed - there’s no permanent extension

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How can you tell a material is elastic from a force-extension curve showing loading and unloading?

A

If both lines start and end in the same position

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What happens when a material is put under tension?

A

The atoms of the material are pulled apart from one another, as atoms can move small distances from their equilibrium position without changing position in the material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What happens to the atoms in a material once a force is removed?

A

The atoms return to their equilibrium distance apart

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

For a metal, elastic deformation happens as long as…?

A

Hooke’s Law is obeyed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is plastic deformation?

A

Where the material is permanently stretched after the force is removed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What happens to the atoms in a material when plastic deformation occurs?

A

Some atoms in the material move position relative to one another. When the load is removed, the atoms don’t return to their original positions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

When does plastic deformation happen with metals?

A

When the metal is stretched past its elastic limit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is tensile stress?

A

The force applied divided by the cross-sectional area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What is a tensile force?

A

A force that stretches something

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What is tensile strain?

A

The change in length divided by the original length of the material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What is the equation for tensile stress?

A

Stress = force / cross-sectional area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What are the units for stress?

A

Pa or Nm^-2

36
Q

What does stress cause?

A

Strain

37
Q

What are compressive forces?

A

Forces that squash a material

38
Q

What is the equation for tensile strain?

A

Strain = extension / original Length

39
Q

What are the units for strain?

A

There are no units because it’s a ratio

40
Q

What happens when a greater tensile force is applied to a material?

A

The stress increases

41
Q

What does the effect of stress on a material do to the atoms of the material?

A

Pulls the atoms apart from one another until eventually the stress becomes so great they separate completely, so the material breaks

42
Q

What is the breaking stress?

A

The stress at which the atoms in a material separate, so the material breaks

43
Q

What is the ultimate tensile stress?

A

The maximum stress that the material can withstand

44
Q

What is the area under a force-extension graph equal to?

A

The elastic strain energy stored in it

45
Q

What is elastic strain energy?

A

The energy stored in a stretched material

46
Q

What is the energy stored in the stretched material equal to?

A

Work done on the material in stretching it

47
Q

What is the equation for elastic strain energy?

A

Energy = 0.5 x stiffness constant x extension^2

48
Q

How can you derive the equation E=0.5FΔL?

A

From a force-extension graph, the energy is the area under the graph. As the area is a triangle (when obeying Hooke’s Law), 0.5 base x height = 0.5FΔL

49
Q

Energy is always…. when stretching?

A

Energy is always conserved when stretching

50
Q

Explain how the conservation of energy works for elastic deformation

A

All the work done is stored as elastic strain energy. When the force is removed, this stored energy is transferred to other forms

51
Q

Explain how the conservation of energy works for plastic deformation

A

Work is done to separate the atoms. The energy is not stored as strain energy, so is mostly dissipated as heat

52
Q

Explain the conservation of energy in springs

A

When a vertical spring with a mass hanging directly below it is stretched, elastic strain energy is stored in the spring. When the end of the spring with the mass is released, energy is transferred to kinetic energy (spring contracts) and gravitational potential energy. The spring then compresses and the kinetic energy is transferred back to elastic strain energy

53
Q

What can the energy changes in an oscillating spring be summed up as?

A

Change in kinetic energy = Change in potential energy

54
Q

Why are modern cars required to have crumple zones that plastically deform?

A

So that the car’s kinetic energy goes into changing the shape of the bumper, so less is transferred to the people inside

55
Q

Up to the limit of proportionality, the stress and strain of a material are…?

A

Up to the limit of proportionality, the stress and strain of a material are proportional to each other

56
Q

What is the Young Modulus?

A

The stress divided by the strain of a material up to the limit of proportionality

57
Q

What is the equation for Young Modulus?

A

E = tensile stress / tensile strain

58
Q

What are the units of Young Modulus?

A

Pa or Nm^-2 (units of stress because strain has no units)

59
Q

What are the 6 steps for the Young Modulus experiment?

A
  • Find cross-sectional area of wire using a micrometer to measure the diameter
  • Clamp the wire to a bench so you can hang weights off the end
  • Start with the smallest weight to straighten the wire (don’t use this in calculations)
  • Measure the distance between the fixed end of the wire and a marker on the wire (this is unstretched length)
  • Add weights to the end in 100g intervals and measure the distance to the marker as above, then calculate the extension
  • Use results to calculate stress and strain then plot a stress-strain graph
60
Q

How do you work out the Young Modulus from a stress-strain graph?

A

Work out the gradient

61
Q

What is the area under a stress-strain graph equal to?

A

The strain energy per unit volume (energy per 1 m^3 o wire)

62
Q

What should the stress-strain graph look like if it is obeying Hooke’s Law?

A

A straight line

63
Q

What is the equation for energy per unit volume?

A

E = 0.5 x stress x strain

64
Q

Describe a stress-strain graph before the limit of proportionality

A

A straight line through the origin, as it is obeying Hooke’s Law. Gradient is constant as it’s the Young Modulus

65
Q

Describe a stress-strain graph after the limit of proportionality

A

The graph starts to bend, as the material is no longer obeying Hooke’s Law, but would return to its original size and shape when stress is removed

66
Q

Describe a stress-strain graph after the elastic limit

A

The graph curves more, as the material starts to behave plastically, so the material would no longer return to its original shape and size

67
Q

Describe a stress-strain graph after the yield point

A

The graph suddenly drops a bit

68
Q

What happens at the yield point?

A

The material suddenly starts to stretch without any extra load.

69
Q

What is the yield point?

A

The stress at which a large amount of plastic deformation takes place with a constant or reduced load

70
Q

When is an example that plastic deformation is useful?

A

If you want to draw copper into long, thin wires

71
Q

What is the difference between a force-extension graph and a stress-strain graph?

A

Force-extension graphs are specific for the tested object, whereas stress-strain graphs describe the general behaviour of the material

72
Q

Why are force-extension graphs specific to the tested object?

A

Because the shape of the graph is affected by the dimensions of the object

73
Q

On a force-extension graph for a wire, how do you draw the unloading?

A

A dotted line which starts at the point the force was removed and is parallel to the loading line

74
Q

What does it mean, on a force-extension graph, if the unloading line doesn’t go through the origin?

A

The object has been deformed plastically so is permanently stretched

75
Q

What is the area between loading and unloading force on a force-extension graph equal to?

A

The work done to permanently deform the wire

76
Q

What does the gradient of a force-extension graph equal?

A

The stiffness constant

77
Q

Describe what the stress-strain graph looks like for a brittle material

A

A straight line with no curves until it stops

78
Q

What happens when the stress-strain graph stops for a brittle material?

A

The material fractures

79
Q

Do brittle materials obey Hooke’s Law?

A

Yes, as the stress-strain graph is a straight line through the origin

80
Q

Describe the force-extension graph for a brittle material

A

A straight line until the material reaches a point where it fractures

81
Q

What happens if you apply a force to a brittle material?

A

Brittle materials don’t plastically deform so they fracture when the force gets too great

82
Q

Why are brittle materials brittle?

A

They have a rigid structure

83
Q

What is a brittle fracture?

A

When a stress applied to a brittle material causes tiny cracks at the material’s surface to get bigger until the material breaks completely

84
Q

What 2 types of atom arrangements are in ceramics?

A

Crystalline and Polycrystalline

85
Q

What is a polycrystalline structure?

A

Where there are many regions of crystalline structure

86
Q

What makes ceramics brittle?

A

The atoms in a ceramic are bonded in a rigid structure

87
Q

What happens in non-brittle materials when a crack appears?

A

The atoms within the material can move to prevent the crack getting larger

A Level Physics Year 1 (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions