measurements and uncertainties

Question 1

6 fundamental quantities and their units and symbols

Answer 1

1. length: metre (m)
2. mass: kilogram (kg)
3. temperature: Kelvin (K)
4. time: seconds (s)
5. current: Ampere (A)
6. amount of substance: mol (mol)

Question 2

Density in fundamental units

Answer 2

kgmˆ-3

Question 3

Energy

Answer 3

kgmˆ2sˆ-2

Question 4

Systematic error

Answer 4

• measurements give identical error for each reading
• cannot be reduced by repetition

Question 5

Example of systematic error + best IB clarification/answer in exam

Answer 5

eg. pointer on a voltmeter does not read zero
- zero offset error

Question 6

Random error

Answer 6

variation of measurements by instrument or operator
- a good experimenter can reduce random error by repetition

Question 7

Example of reducing random error

Answer 7

repeating pendulum oscillation times
or
measuring diameter of a wire many times in different positions

Question 8

Accuracy

Answer 8

values are close to the accepted value
- they have a small systematic error

Question 9

precision

Answer 9

precise values are close to each other
- they have a small random error

Question 10

how to calculate uncertainty based on repeated values

Answer 10

find the average.
biggest value - average value
= average result +- calc. uncertainty

Question 11

Uncertainties should not have greater _______ than the value

Answer 11

resolution
eg. 2.34 +- 0.02
NOT
2.34 +- 0.0002

Question 12

Uncertainties are normally quoted to how many significant figures?

Answer 12

1

Question 13

what makes a good table

Answer 13

• starting with 0.00
• units in heading
• repeating many times
• wide range
• calculated average
• consistency in d.p. columns

Question 14

A proportional graph is….

Answer 14

• a straight line
  and
• through the origin