Topic 1: Physics and physical measurement

Question 1

Smallest magnitude of distance

Answer 1

10^-15 m (sub-nuclear particles)

Question 2

Largest magnitude of distance

Answer 2

10²⁵ m (extent of the visible universe)

Question 3

Smallest magnitude of mass

Answer 3

10^-30 kg (electron)

Question 4

Largest magnitude of mass

Answer 4

10⁵⁰ kg (mass of the universe)

Question 5

Smallest magnitude of time

Answer 5

10^-23 s (passage of light across a nucleus)

Question 6

Largest magnitude of time

Answer 6

10¹⁸ s (age of the universe)

Question 7

SI unit for mass

Answer 7

kilograms, kg

Question 8

SI unit for distance

Answer 8

metres, m

Question 9

SI unit for time

Answer 9

seconds, s

Question 10

SI unit for amount of substance

Answer 10

mole, mol.

Question 11

SI unit for electric current

Answer 11

ampere, A

Question 12

SI unit for temperature

Answer 12

kelvin, K

Question 13

What unit is used when calculating the cost of heating?

Answer 13

kW h

Question 14

1 J = ? eV

Answer 14

1 elementary charge

Question 15

Define: random error

Answer 15

Errors in measurement that lead to measurable values being inconsistent when repeated measures of a constant attribute or quantity are taken.

Question 16

Sources of random error (4)

Answer 16

1. unpredictable fluctuations in the readings of a measurement apparatus
2. the experimenter’s interpretation of the instrumental reading
3. effects of a change in the surroundings
4. readability of the instrument

Question 17

Define: systematic error

Answer 17

An error that is not determined by chance but is introduced by an inaccuracy (as of observation or measurement) inherent in the system.

Question 18

Sources of systematic error (2)

Answer 18

1. an instrument with zero error
2. a wrongly calibrated instrument

Question 19

Define: precision

Answer 19

A measurement of how close a number of measurements of the same quantity agree with each other. It is limited by random error.

Question 20

Define: accuracy

Answer 20

How close the measurement is to the true value of the quantity being measured. It is reduced by systematic error.

Question 21

How can random errors be reduced?

Answer 21

By repeated readings.

(N.B. systematic error cannot be reduced by repeat readings)

Question 22

How can absolute uncertainty be calculated?

Answer 22

When marking the absolute uncertainty in a piece of data, we simply add ± 1 of the smallest significant figure.

Question 23

How can fractional uncertainty be calculated?

Answer 23

To calculate the fractional uncertainty of a piece of data we simply divide the uncertainty by the value of the data.

Question 24

How can percentage uncertainty be calculated?

Answer 24

To calculate the percentage uncertainty of a piece of data we simply multiply the fractional uncertainty by 100.

Question 25

Determine the uncertainties in addition and subtraction.

Answer 25

When performing additions and subtractions we simply need to add together the absolute uncertainties.

Question 26

Determine the uncertainties in multiplication and division

Answer 26

When performing multiplications and divisions we simply add together the percentage uncertainties.

Question 27

Determine the uncertainties in powers.

Answer 27

Multiply the uncertainty by the power

Question 28

Define: vector quantity

Answer 28

A quantity with magnitude and direction

Question 29

Define: scalar quantity

Answer 29

A quantity with only magnitude