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A-level AQA Physics > 09 Materials > Flashcards

09 Materials Flashcards

(84 cards)

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1
Q

What is the definition of density?

A

Mass per unit volume.

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2
Q

What is the equation of density?

A

Mass / volume (m/v)

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3
Q

What is the unit for density?

A

Kg m^-3 or g cm^-3

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4
Q

What is the symbol of density?

A

p

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5
Q

What is the density of pure water?

A

1000kg m^-3

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6
Q

What is the definition of precision?

A

The smallest non-zero reading that can be measured.

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7
Q

What does the uncertainty have to be bigger than?

A

The instruments precision.

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8
Q

When a quantity is found by raising another quantity to a power,how do you get the percentage uncertainty?

A

Multiply the percentage uncertainty of the original quantity by the power.
eg- d^3 —> %Ud x 3

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9
Q

When a quantity in multiplied or divided by another, how do you find the combined percentage uncertainty?

A

Add the values together.

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10
Q

If there is no range then what is the uncertainty?

A

The same as the precision

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11
Q

What does vernier mean?

A

2 scales that cross

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12
Q

How do you use a vernier micrometer?

A

•take a reading close to the jaws using the ratchet.
•read the main scale reading from the barrel and add this value to micrometer reading on the thimble where the 2 scales meet

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13
Q

How do you use vernier callipers?

A

Start by looking at where the 0 on the bottom scale meets the other scale. This gives the mm’s. Then look at which line on the bottoms scale lines up perfectly with the main scale. This gives the 100th’s of a mm.

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14
Q

What is this?

A

Digital callipers

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15
Q

What is this?

A

A vernier micrometer.

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16
Q

What is this?

A

Vernier callipers

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17
Q

What is Hooke’s law?

A

Hooke’s law is obeyed if extension is directly proportional to the stretching force provided the limit of the proportionality has not been exceeded.

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18
Q

What is the definition of spring constant?

A

The stretching force per unit extension.

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19
Q

What is the symbol for spring constant?

A

k

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20
Q

What is spring constant (k) measured in?

A

N m‐1.

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21
Q

What error does a set square avoid?

A

Parallax error.

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22
Q

What is the independent variable for the Hooke’s law practical?

A

The mass / force / weight.

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23
Q

What is the dependent variable of the Hooke’s law practical?

A

Extension

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24
Q

What is the control variable of the Hooke’s law practical?

A

Use the same spring.

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25
In the Hooke's law practical, how do you ensure that the ruler is vertical?
Use a **spirit level** or set square.
26
What is a source of error in the Hooke's law experiment? *not parallax *
Masses aren't the correct mass
27
As a spring stretches what happens to the force needed to stretch it?
It increases
28
Where is elastic strain energy stored?
In a stretched string
29
What is the area between the line and the extension axis equal to in a force vs extension graph?
The energy stored in a spring that has been stretched by an amount equal to ΔL
30
What in tension in P + tension in Q equal to?
The weight
31
What is the tension in each spring equal to?
½ weight
32
What is the extension of each spring compared with if it was a single spring supporting the weight?
½
33
What is the spring constant of a parallel combination of 2 identical springs?
Double that of a single spring.
34
What is the tension of each spring equal to?
The weight
35
What is the extension of each spring compared with if it was a single spring supporting the weight?
The same
36
What is the extension of the combination compared to that if a single spring?
Double
37
What is the spring constant of a series combination of two springs half of?
The spring constant of a single spring.
38
What type of line on a force vs extension graph should a material which obeys hookes law produce?
A straight line through the origin.
39
What happens to an elastic material after it has been stretched and the load has been removed?
It returns to its original length.
40
What is a material which has a permanent stretch once the load has been removed said to have?
To have been stretched beyond its elastic limit and has shown plastic behaviour.
41
What is the area between the loading curve and the extension axis equal to in a force vs extension graph?
The energy stored in the stretched material.
42
What is the area between the unloading curve and the extension axis equal to in a force vs extension graph?
The energy used to lift the load each time a mass is removed from the hanger.
43
What is the shaded area called?
A hysteresis loop
44
What is the difference between the loading and the unloading areas equal to on a force vs extension graph?
The energy converted to heat in the rubber band during the experiment.
45
What is sample rate also known as?
Sampling frequency.
46
What is sample rate?
It refers to the number of samples taken per unit of time. (Data logger).
47
What is sample rate measured in?
Hz
48
What is an alternative method of measuring the spring constant of a spring?
By using a force-sensor to measure the stretching force applied to the spring. The distance-sensor measures the extension of the spring.
49
What is an advantage of using a data logger for the hookes law experiment?
Removes reaction time error.
50
51
What is the experiment to determine the spring constant of a spring?
-Determine the extension of the spring when attaching masses from 100g - 450g in 50g intervals. Do for both loading and unloading. -Align the side of the ruler with one edge of the set square. -Position the bottom of the spring on the other edge of the set square (to prevent the parallax error) and measure the reading from the ruler. -Each time the spring is stretched, determined the extension by subtracting the original measurement from the new measurements.
52
What is the definition of tensile stress?
Tensile stress is the stretching force per unit cross-sectional area.
53
What are the units for tensile stress?
N m‐² or Pa.
54
What is the definition for tensile strain?
Extension divided by its original length.
55
What is the definition of young's modulus?
Tensile stress divided by tensile strain. (Before the limit of proportionality)
56
What are the units for young's modulus?
N m-² or Pa
57
When is there a bigger youngs modulus value?
With a stiffer material.
58
On a force vs extension graph, what is the area between the line and the extension axis give?
The energy stored in the stretched wire.
59
What does stretching a wire stretch?
The bonds between the atoms.
60
When removing the stretching force, what does the wire return to?
It's original length.
61
On stress vs strain graph, at what point does the curve end?
At the point that the material fractures.
62
What is the breaking stress?
The stress that breaks the material.
63
Can a ductile material be permanently stretched well beyond its elastic limit without breaking?
Yes. It undergoes plastic deformation.
64
What happens to a brittle material when there is a very small increase in strain beyond the linear section?
It fractures.
65
What does a brittle material break without ?
Any plastic deformation.
66
What is the gradient of the straight section ?
F/ΔL = stiffness.
67
What is the gradient of the straight section?
Stress/strain = Young's modulus.
68
What is E in the equation?
Young's modulus.
69
What does πr² mean in the equation?
The cross-sectional area.
70
What does L mean in the equation?
Original length.
71
What does ΔL mean in the equation?
Change in length / extension.
72
What is the equation for young's modulus?
73
Describe the equipment for the experiment to stretch a copper wire?
74
In the stretching a copper wire experiment, does the wire show elastic properties?
Yes.
75
What is spring constant also known as?
Stiffness.
76
On the stretching copper wire experiment, on a force vs extension graph, what property of the wire does the initial gradient represent?
The spring constant / stiffness of the wire.
77
On the stretching copper wire experiment, what would happen to the gradient of the force vs extension graph if a thicker wire had been used?
It would be steeper.
78
What is the limit of proportionality?
The point on the force vs extension graph just before the initial straight line starts to bend .
79
What is the elastic limit?
The greatest amount that a material can be stretched and still return to its original length.
80
What materials are described as a ductile material?
A material which stretches a lot after it's elastic limit.
81
What materials are described as a brittle material?
A material which breaks soon after reading it's elastic limit.
82
When does plastic deformation occur?
When a material has been stretched beyond its elastic limit. This means that the material no longer returns to its original length. There is a permanent extension.
83
When a wire is unloaded, why is the unloading line is straight and has the same gradient as straight section of the loading line?
Because there are identical forces between bonds.
84
What does the enclose area on the diagram give?
The amount of energy changed to heat after the loading/ unloading process has been completed.

A-level AQA Physics (13 decks)

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