Module 2 - Foundation of physics (Measurements and Uncertainties)

Question 1

What are the conventions for labelling table columns

Answer 1

1 - There must be a column heading
2 - The must be both a quantity and a unit in the column heading
3 - Quantities must be written in symbols or words
4 - There must be a distinguishing mark between the quantity and the unit (/)

Question 2

What is meant by the term error

Answer 2

An error is the difference between the measured value and the ‘correct result’

Question 3

What are errors caused by

Answer 3

Measuring instruments, or design of experiment

Question 4

What is meant by a Random Error

Answer 4

Measurement errors whereby the measurements vary unpredictably

Question 5

What are 2 causes of Random Errors

Answer 5

• External Factors that are not controlled in the experiment skew the results.
• Difficulty taking a reading because of the measuring equipment

Question 6

You can correct Random Errors (True/False)

Answer 6

False - But its effect can be mitigated by taking repeat readings and taking a mean

Question 7

What is meant by a Systematic Error

Answer 7

Measurement erros where measurements differ from the true value by a consistent amount each time.

Question 8

What are 2 reasons for Sytematic Errors

Answer 8

1 - The method in which the measurements are taken is flawed
2 - Faulty measuring devices that cause a ‘zero error’

Question 9

What is a Zero Onset Error

Answer 9

When the reading doesn’t equal zero when the quantity being measured is zero

Question 10

You can correct Sytematic Error (True/False)

Answer 10

True - by calibration (use a know value and take the difference between it and the given value from the measuring device)

Question 11

1. How would you spot a systematic error on a graph
2. Do systematic errors skew trends if (yes/no) explain

Answer 11

1. If the theory and the results don’t match i.e a zero error on a graph.
2. No, because the measurements differ by the same value each time so the gradient when plotted will be consistent

Question 12

What is the difference between how numbers are rounded or given in a table as opposed to in calculations

Answer 12

In a table, measurements are given to have the same number of decimal places, but in a calculation the measurements are given to the same number of significant figures

Question 13

What is meant by the term accuracy

Answer 13

How close the measurement is to the true value

Question 14

What is meant by the term precision

Answer 14

How close repeated measurements are to each other

Question 15

What is meant by the term Resolution

Answer 15

The smallest increment an instrument can measure

Question 16

What is the relationship between instrument increments and resolution

Answer 16

small increments - high resolution
large increments - low resolution

Question 17

What is meant by the term Reproducability

Answer 17

Testing an experiment multiple times for results that return the same value under similar conditions

Question 18

What is meant by the term Repeatability

Answer 18

Testing an experiment multiple times for results that return the same value under the same conditions

Question 19

what is the equation for percentage uncertainty

Answer 19

% uncertainty = (absolute uncertainty x 100 / measured value)

Question 20

What is the absolute uncertainty of an instrument that measures length if a range of values are taken.

Answer 20

absolute uncertainty = half the range of values.

Question 21

What is the absolute uncertainty of an instrument that measures length if only one measurement is taken or multiple values give the same result.

Answer 21

absolute uncertainty = resolution of instrument.

Question 22

When doing calculations involving uncertainties what are the three rules for uncertainty manipulation.

Answer 22

1. when quantities are added there absolute uncertainties are added together.
2. when quantities are multiplied together there percentage uncertainties are added together.
3. when a quantity is raised to the power of n the percentage uncertainty is multiplied by n.

Question 23

What are the 5 points graphs are given credit for

Answer 23

1. choice of scales
2. plotting point
3. lines of best fit.
4. calculating gradients
5. determination of y-intercept

Question 24

Tips for choosing scales

Answer 24

Use more frequent intervals that go up by the same quantity.
Dont use scales of prime numbers except 2 and 5

Question 25

Tips for plotting points

Answer 25

Use a sharp pencil, and use an x to mark the point with a 1/2 box lenience

Question 26

tips for line of best fit

Answer 26

There must be an equal distribution of plotted points above and below the line

Question 27

Calculating Gradients

Answer 27

1 - gradient = change in y / change in x 2 - use a triangle that takes up at least half of the line

Question 28

Determining the y-intercept

Answer 28

The y-intercept is when x=0, so use the y=mx+c form equation, especially when either axis doesn't start at 0, and substitue x=0 into the equation.

Question 29

What is the line of worst fit and the 2 different types

Answer 29

The line of worst fit shows extreme but still valid trends of data that must go between errorbars. There are 2 types one that is the steepest showing the max garadient and the shallowest that shows the min gradient.

Question 30

What are error bars

Answer 30

Graphical representation of absolute uncertainties

Question 31

How to calculate uncertainties from a graph

Answer 31

Subtract the gradient of one of the lines of worst fit from the gradient of the line of best fit.

Question 32

What is an uncertainty

Answer 32

An interval that we can expect the true value to lie within.