Topic 1: Measurements and uncertainties

Question 1

What is precision?

Answer 1

how well repeated measurements of a value agree with one another (exact)

Question 2

What is accuracy?

Answer 2

how well a measurement agrees with the true value (correct)

Question 3

When using an analog scale, what is the uncertainty?

Answer 3

plus or minus half the smallest scale division

Question 4

When using a digital scale, what is the uncertainty?

Answer 4

plus or minus the smallest unit shown

Question 5

When taking repeated measurement how do you find the uncertainty?

Answer 5

find the difference between the average and the measurement that is furthest from the average

Question 6

What is the order of magnitude for the size of subatomic particles to the extent of the visible universe?

Answer 6

10^-15 m to 10^25 m

Question 7

What is the order of magnitude for the mass of the electron to the mass of the universe?

Answer 7

10^-30 kg to 10^50 kg

Question 8

What is the order of magnitude for time for light to cross a nucleus to the age of the Universe?

Answer 8

10^-23 s to 10^18 s

Question 9

What is the order of magnitude for the size of a hydrogen atom?

Answer 9

10^-10 m

Question 10

What is the order of magnitude for the size of a proton?

Answer 10

10^-15 m

Question 11

What is the ratio of diameter of a hydrogen atom to its nucleus?

Answer 11

10^-10/10^-15 = 10^5

Question 12

What is displacement?

Answer 12

the distance moved in a stated direction (the distance and direction from the starting point)

Question 13

What is velocity?

Answer 13

the rate of change of displacement

Question 14

What is acceleration?

Answer 14

the rate of change of velocity

Question 15

What is instantaneous speed/velocity?

Answer 15

the change in distance/displacement divided by time at one particular time

Question 16

What is a frame of reference?

Answer 16

a point from which a situation is observed

Question 17

What are systematic errors and examples of them?

Answer 17

Systematic errors are constant errors that are due to faults in the system used to measure a variable.

Examples are miscalibration, wearing down over time, or a constant delay in every reading.

They will be precise but not accurate.

Question 18

What are random errors and examples of them?

Answer 18

Random errors can occur in any method of measuring but happen primarily when estimating.

These will differ from trial to trial and are not precise.

For example, measuring the speed of sound when making a loud clap a distance from the wall might cause a random error due to the reaction time of the experimenters measuring the time it takes the sound to travel.

Question 19

What are absolute uncertainties?

Answer 19

When the uncertainty is given in the same unit as the answer given and should be written to the same number of decimal places.

E.g. 294.56 ± 3.01 N

Question 20

What are fractional uncertainties?

Answer 20

When the uncertainty is given as a fraction of the original quantity. It is dimensionless (without units).

E.g. 2.6 ± 0.2 = 2.6 ± (0.2/2.6 or 0.077)

Question 21

What are percentage uncertainties?

Answer 21

When the uncertainty is given as a percentage of the original quantity. You can get this from multiplying the fractional uncertainty by 100.

E.g. 2.6 ± 0.2 = 2.6 ± 7.7%

Question 22

What is the combination of the uncertainties of different quantities called?

Answer 22

Propagation of uncertainties

Question 23

What do you do to the uncertainty of two values when you multiply or divide them?

Answer 23

You add their fractional or percentage uncertainties.