Unit 1 Measurements and their errors

Question 1

Name the six SI base quantities and their units.

Answer 1

Mass (kilogram)
length (metre)
time (second)
electric current (ampere)
temperature (kelvin)
Amount of substance (mole)

Question 2

State the name, symbol and multiplying factor for each of the SI prefixes from tera to kilo

Answer 2

Tera (T) x10^12
Giga (G) x10^9
Mega (M) x10^6
Kilo (k) x10^3

Question 3

State the name, symbol and multiplying factor for each of the SI prefixes from centi to femto

Answer 3

• Centi (c) x10^-2
• Milli (m) x10^-3
• Micro x10^-6
• Nano (n) x10^-9
• Femto (f) x10^-15

Question 4

What is the uncertainty in a measurement of a quantity?

Answer 4

The difference between the measured value and the true value of the quantity

Question 5

What is the absolute uncertainty of a measurement?

Answer 5

Possible difference from the true value given as a fixed number in the unit of measurement

Question 6

What is the percentage uncertainty of a measurement?

Answer 6

Possible difference from the true value given as a percentage of the measurement

Question 7

How are the uncertainties combined when two or more measurements are added or subtracted?

Answer 7

Absolute uncertainties are added together

Question 8

How are the uncertainties combined when two or more measurements are multiplied or divided by each other?

Answer 8

Percentage uncertainties are added together

Question 9

How is the uncertainty found when a measurement is raised to a power?

Answer 9

Percentage uncertainty is multiplied by the power

Question 10

What do error bars on a graph represent?

Answer 10

Uncertainties in measurement data

Question 11

What can worst fit lines on a graph be used for?

Answer 11

Finding the uncertainty in the gradient and intercepts of a straight line graph

Question 12

How can the uncertainty in the gradient of a straight line graph be found?

Answer 12

From the biggest difference between the gradient of the best fit and worst fit lines

Question 13

redo this card

What is a random error?

Answer 13

Error that causes readings to be spread about the true value due to results varying in an unpredictable way between measurements

Question 14

What is a systematic error?

Answer 14

Error that causes readings to be different from the true value by a consistent amount

Question 15

What is a zero error?

Answer 15

An instrument that does not read zero when it should

Question 16

What is an accurate measurement?

Answer 16

A measurement that is close to the true accepted value

Question 17

What is a precise measurement?

Answer 17

Measurement where there is very little spread about the mean

Question 18

What are repeatable measurements?

Answer 18

Measurements where the same results are obtained if the original experimenter repeated the measurements using the same equipment and method

Question 19

What are reproducible measurements?

Answer 19

Measurements where similar results are obtained if a different experimenter carries out the measurements using a different method and/or equipment

Question 20

What is the resolution of a measuring instrument?

Answer 20

Smallest change in the quantity being measured that the instrument can detect