Workbook 1 - Measurements and Their Errors

Question 1

What are S.I. units?

Answer 1

A coherent system of units that all fit together. When doing calculations you need to convert measurements in S.I. units.

Question 2

What are the 7 fundamental S.I. units?

Answer 2

1. Ampere (A), the unit of electrical current
2. Candela (cd), the unit of luminous intensity
3. Kelvin (K), the unit of temperature
4. Kilogram (Kg), the unit of mass
5. Metre (m), the unit of length
6. Mole (mol), the unit of quantity of a substance (how many atoms or molecules)
7. Second (s), the unit of time

Question 3

Other important S.I. units?

Answer 3

Speed - ms^-1
Area - m^2
Volume - m^3
Force (Newtons) - N or kgms^-2
Energy (Joules) - J or kgm^2s^-2

Question 4

What are the 10 prefixes?

Answer 4

• Tera - T - 10^12
• Giga - G - 10^9
• Mega - M - 10^6
• Kilo - k - 10^3
• Centi - c - 10^-2
• Milli - m - 10^-3
• Micro - mu - 10^-6
• Nano - n - 10^-9
• Pico - p - 10^-12
• Femto - f - 10^-15

Question 5

Definition of accuracy?

Answer 5

A measurement result is considered accurate if it is judged to be close to the true value

Question 6

What is calibration?

Answer 6

Marking a scale on a measuring instrument. This involves establishing the relationship between indications of a measuring instrument and standard or reference quantity values, which must be applied. For example, placing a thermometer in melting ice to see whether it reads 0 degrees, in order to see if it has been calibrated correctly

Question 7

What is data?

Answer 7

Information, either qualitative or quantitative, that has been collected

Question 8

What is measurement error?

Answer 8

The difference between a measured value and the true value

Question 9

What are anomalies?

Answer 9

These are values in a set of results which are judged not to be part of the variation caused by random uncertainty

Question 10

What is random error?

Answer 10

These cause readings to be spread about the true value, due to results varying in an unpredictable way from one measurement to the next. The effect of random errors can be reduced by taking more measurements and calculating a mean.

Question 11

What is systematic error?

Answer 11

These cause readings to differ from the true value by a consistent amount each time a measurement is made.

Question 12

Zero error?

Answer 12

An indication that equipment gives a false zero reading

Question 13

What is evidence?

Answer 13

Data which has been shown to be valid

Question 14

What is a fair test?

Answer 14

A test in which only the independent variable has been allowed to affect the dependent variable

Question 15

What is a hypothesis?

Answer 15

A proposal intended to explain certain facts or observations

Question 16

What is interval?

Answer 16

The quantity between readings

Question 17

What is precision?

Answer 17

Precise measurements are ones in which there is very little spread about the mean value. It depends only on the extent of random errors

Question 18

What is a prediction?

Answer 18

A prediction is a statement suggesting what will happen in the future, based on observations, experience or a hypothesis

Question 19

What is the range?

Answer 19

The maximum and minimum values of the independent or dependent variables. It is important in ensuring that any pattern is detected

Question 20

When are measurements repeatable?

Answer 20

If the original experiment repeats the investigation using the same method and equipment and obtains the same results.

Question 21

When is a measurement reproducible?

Answer 21

If the investigation is repeated by another person or by using different equipment or techniques and the same results are obtained

Question 22

What is resolution?

Answer 22

This is the smallest change in the quantity being measured (input) of a measuring instrument that gives a perceptible change in the reading

Question 23

What is a sketch graph?

Answer 23

A line graph that generally shows the shape and relationship between two variables. Doesn’t have any points plotted but does need labeled axes

Question 24

What is the true value?

Answer 24

The value that would be obtained in an ideal measurement

Question 25

What is uncertainty?

Answer 25

The interval within which the true value can be expected to lie, with a given level of confidence or probability

Question 26

What is validity?

Answer 26

Suitability of the investigation procedure to answer the question being asked

Question 27

What is a valid conclusion?

Answer 27

A conclusion supported by valid data, obtained from an appropriate experimental design and based on sound reasoning

Question 28

What are categoric variables?

Answer 28

Values that are labels

Question 29

What are continuous variables

Answer 29

Continuous variables can have values that can be given a magnitude either by counting or by measurement

Question 30

What are control variables?

Answer 30

A control variable is one which may, in addition to the independent variable, affect the outcome of the investigation and therefore has to be kept constant or at least monitored

Question 31

What are dependent variables?

Answer 31

A variable of which the value is measured for each and every change in the independent variable

Question 32

What are independent variables?

Answer 32

Variable for which values are changed or selected by the investigator

Question 33

How do you read a micrometer?

Answer 33

The scale on the sleeve is in millimeters, the scale on the thimble is in 1/100ths of a mm. 1 full rotation is 0.5mm

Question 34

How do you calculate the percentage error of T=2.0s +/- 0.1s?

Answer 34

0.1/0.2 x 100

Question 35

What is the equation that can be given for a simple pendulum?

Answer 35

T = 2pi x square root (l/g)

Question 36

What is the equation for percentage error?

Answer 36

Percentage error = error/true value x 100

Error = measured value-true value

Question 37

What is Hooke’s Law?

Answer 37

Extension from the natural length is proportional to the force applied up until the limit of proportionality

Question 38

Why is an estimate not just a guess?

Answer 38

Because it is the result of a calculation where some of the data used is based on typical values