Practical Skills Flashcards

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1
Q

What is resolution of a measuring device?

A

The smallest division on the scale

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2
Q

In experiments what is precision?

A

A measure of the spread of the values about a mean value
(high presiscion = small spread)

Random errors determine precision of data

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3
Q

How is precision different to accuracy?

A

Precision is how close the values are to a mean value

Accuracy is how close that mean value is to the actual value

Results can be precise but inaccurate (eg with a systematic error)

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4
Q

What makes a measurement accurate?

A

If it is close to the true value (within its absolute uncertainty)

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5
Q

What is a measurement error?

A

Taking a reading and that is different to the actual value
(caused by random or systematic errors)

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6
Q

What are the 2 types of measurement errors?

A

**1. Random
2. Systematic **
Subcategories: zero, callibration, parallax, reaction time

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7
Q

What is an anomaly?

A

An incorrect measurement outside of the range of uncertainty

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8
Q

How do you deal with anomalies in results?

A
  • Repeat measurement if possible
  • If not discount anomalous result
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9
Q

What is a random error?

A

Something that causes results to be randomly spread out around a true value (eg repeat measurements for freefall)

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10
Q

How do you reduce random errors in experiments?

A

Take repeat measurements and calculate averages

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11
Q

What is a systematic error?

A

An error that causes all results to be affected by the same amount (eg reaction time using stopwatch)

Can be caused by miscalibrated equipment (zero error)

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12
Q

How do you reduce systematic errors in experiments?

A

Ensure equipment is correctly calibrated

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13
Q

What is a parallax error?

A

The viewing angle affects the measurement

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14
Q

What 2 things do you do to reduce parallax errors in experiments?

A
  1. Bring eyeline as level with scale as possible
  2. Place measuring equipment as close to object as possible
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15
Q

What type of error is this?

A

Random error (Reduced taking repeats and average)

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16
Q

What type of error is this?

A

Parallax

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17
Q

What type of error is this?

A

Systematic

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18
Q

What kind of error is this?

A

Systematic

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19
Q

What makes an experiment a fair test?

A

Only one variable is changed (independent variable) to affect the dependent variable

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20
Q

For a scientific result to be accepted what 2 conditions must the experiment meet?

A
  1. Repeatable - If you can perform the experiment again and get the same result
  2. Reproducible - If someone else can perform the same experiment and get the same result
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21
Q

In experimental science what is absolute uncertainty?

A

The interval which the actual value of a measurement is expected to lie in

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22
Q

How is absolute uncertainty for a measurement determined?

A
  • = resolution of equipment
    or
  • Half range of repeats (discount anomalies)
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23
Q

What is the absolute uncertainty here?

A

±1𝑚𝑚
(measurement = resolution)

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24
Q

What is the absolute uncertainty here?

A

±0.005V
(reading = half resolution)

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25
Q

What is the absolute uncertainty here?

A

±0.05s

26
Q

What is the reading on this venier scale?

A

10.02cm

27
Q

What is the reading on this venier scale?

A

3.34cm

28
Q

What is the reading on this micrometer scale?

A

10.83mm

29
Q

What is the reading on this micrometer scale?

A

2.88mm

30
Q

How do you calculate percentage uncertainty?

A
31
Q

How do you combine uncertainties for measurements with different units?

A

Add together their percentage uncertanties

Do not add together their absolute uncertainties

32
Q

How do you combine uncertainties for measurements with the same units?

A

Add together their absolute uncertanties

Do not need to add together their percentage uncertainties

33
Q

What has been done wrong here?

A

Cannot add together absolute uncertainties if units are different

Must only add together percentage uncertainties

34
Q

What has been done wrong here?

A

Anomalous result shouldn’t have been included

35
Q

What do error bars show?

A

Graphically shows absolute uncertainty in one of the measurements
(x or y axis)

36
Q

What do error boxes show?

A

Graphically shows absolute uncertainty in both of the measurements
(x and y axis)

37
Q

What is the absolute uncertainty in this reading?

A
38
Q

How do error bars help with analysing results?

A
  1. Visually show precision of experiment
  2. Help identify anomalous results
  3. Allow more precise gradient line to be drawn
39
Q

How do you work out the percentage uncertainty of a gradient?

A
40
Q

How do you work out the percentage uncertainty of a y-intercept?

A
41
Q

How do you combine these uncertainties?

A
  1. Add together percentage uncertainties
  2. Multiply power by corresponding percentage uncertainty
42
Q

How do you combine these uncertainties?

A
  1. Add together percentage uncertainties
  2. Multiply power by corresponding percentage uncertainty
43
Q

Which of these experiments is more successful?

A

g2. As the actual value is within it’s absolute uncertainty

44
Q

What is wrong here?

A

Absolute uncertainties must match decimal points of measurements

45
Q

What is wrong here?

A

Calculated values can’t have higher precison than source values

46
Q

What is wrong here?

A

Units should be put in the column headings

47
Q

What is wrong here?

A

Values in each column should have the same number of decimal places

48
Q

What is wrong here?

A

Scale should go up in 1s, 2s or 5s

49
Q

What is wrong here?

A

Axis need titles and units

50
Q

What is wrong here?

A

Data take up less than half of the page
Instead ** use a broken axis if possible**

51
Q

What is wrong here?

A

Data points should always be plotted with crosses (not dots)

52
Q

What is wrong here?

A

Don’t force Line of Best Fit through origin

53
Q

What is wrong here?

A

Gradient triangle should be as large as possible

54
Q

How do you reduce the percentage uncertainty of a measurement?

A
  1. Use measuring device with higher precision
  2. Take bigger measurements (eg use bigger distances in experiment)
55
Q

In this SHM experiment why is time measured over 10 oscillations?

A

Reduces absolute uncertainty of each oscillation by 10x

56
Q

In this double slit experiment why is distance measured between 11 dots?

A

Reduces absolute uncertainty of each distance by 10x

57
Q

How do you calculate fractional uncertainty?

A
58
Q

How is absolute uncertainty for a reading determined?

A
  • =Half resolution of equipment
  • =Half range of repeats (ignoring anomalies)
59
Q

What is the difference between a reading and a measurement?

A

Reading - 1 judgement
Measurement - 2 judgements to calculate value (usually for distances and angles)

Absolute uncertianties for measurements = 2 x uncertainties for readings

60
Q

How do you calculate the absolute uncertainty in a y-intercept?

A
61
Q

How do you calculate the absolute uncertainty in a gradient?

A