Measurements and error

Question 1

Orders of magnitude

Answer 1

• 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 (µ) - 10^-6
• Nano (n) - 10^-9
• Peko (p) - 10^-12
• Fento (f) - 10^-15

Question 2

How do we reduce random errors?

Answer 2

• Repeating the measurement
• Finding a mean

Question 3

How do you reduce systematic errors?

Answer 3

• Redo the experiment using a different method
• Use different instruments

Question 4

What does accuracy mean?

Answer 4

• How close your result is to the true value

Question 5

What does precision mean?

Answer 5

• How close your readings are together

Question 6

What is the difference between reeatable and reproducable?

Answer 6

• Repeatable: you can do the experiment again and get the same results
• Reproducable: someone else can do the experiment again and get the same results

Question 7

What is resolution?

Answer 7

• The smallest change in the quantity being measured that gives a change in the reading on the instrument

Question 8

What are the different types of uncertainty?

Answer 8

• Absolute uncertainty: fixed quantity
• Fractional uncertainty: uncertainty is a fraction of the measurement
• Percentage uncertainty: uncertainty is a percentage of the measurement

Question 9

How to calculate percentage and fractional uncertainty

Answer 9

• Percentage uncertainty = (uncertainty / measured value) x 100
• Fractional uncertainty = percentage uncertainty / 100

Question 10

What is the difference between a reading and a measurement?

Answer 10

• A reading is when you make 1 judgement. E.G: a thermometer
• A measurement is when you make 2 or more judgements. E.G: a ruler (you must judge where the start AND end point is)

Question 11

Uncertainties in readings and measurements

Answer 11

• Uncertainty in reading is ± half of the smallest scale division
• Uncertainty in measurement is ± the smallest scale division

Question 12

Uncertainties in repeated data and digital readings

Answer 12

• Uncertainty in repeated data is ± half of the range
• Uncertainty in digital readings is ± the last significant digit

Question 13

How do you combine uncertainties when you are adding or subtracting data?

Answer 13

• Add together the absolute uncertainties

Question 14

How do you combine uncertainties when you are multiplying or dividing data?

Answer 14

• Add the percentage or fractional uncertainties

Question 15

How do you combine uncertainties when you are raising to the power?

Answer 15

• Multiply the percentage uncertainty by the power

Question 16

How to find percentage uncertainty from line of best fit

Answer 16

Percentage uncertainty = (y intercept of line of best fit - worst y intercept) / best y intercept