2. FOUNDATIONS IN PHYSICS

Question 1

Write down everything you know about Prefixes
(2)

Answer 1

P - peta - 10^15
T - tera - 10^12
G - giga - 10^9
M - mega - 10^6
k - kilo - 10^3
d - deci - 10^-1
c - centi - 10^-2
m - milli - 10^-3
u - micro - 10^-6
n - nano - 10^-9
p - pico - 10^-12
f - femto - 10^-15

prefix —> no prefix = x
no prefix —> prefix = ÷

Question 2

Write down everything you know about Errors
(2)

Answer 2

RANDOM ERRORS
(e.g. anomalies)
- unpredictable
- effects the gradient of a graph
- take multiple measurements to reduce the effect

SYSTEMATIC ERRORS
(e.g. zero error, parallax)
- effects all measurements by the same amount, displaces the gradient

Question 3

Write down everything you know about Uncertainties
(5)

Answer 3

ABSOLUTE UNCERTAINTY
From a range of numbers:
1. Find the range
2. Divide the range by 2
3. Find the mean value
4. Mean value ± half the range
From a device:
The smallest scale it measures

PERCENTAGE UNCERTAINTY
(absolute uncertainty ÷ value) x 100%

COMBINING UNCERTAINTIES
Values with the same units/addition or subtraction:
1. Add values together
2. Add absolute uncertainties together
3. Combine
Values with different units/multiplication or division:
1. Work out value (x or ÷)
2. Add the individual %uncertainties together
3. Percentage uncertainty of the combined value = absolute uncertainty

UNCERTAINTIES WITH POWERS
%uncertainty in y^n = n x %uncertainty in y

UNCERTAINTY OF A GRAPH
((gradient of best line - gradient of worst line) ÷ gradient of best line) x 100%
= %uncertainty
(worst line = shallowest or steepest line)
numerator of fraction = absolute uncertainty

Question 4

Write down everything you know about Tables
(2)

Answer 4

Headings of table columns should show the quantity and the unit (e.g. time/s)

All values must be measured to the same number of significant figures

Question 5

Write down everything you know about Graphs
(3)

Answer 5

LAYOUT
- independent variable on x-axis
- dependent variable on y-axis
- axis labelled with quantity and unit (e.g. time/s)
- graph must cover 75% of space provided

CALCULATING GRADIENT
1. Draw a straight line of best fit (tangent if graph is a curve)
2. Calculate using a triangle that covers at least 75% of the graph. (done use original data points)

UNCERTAINTY OF A GRAPH
((gradient of best line - gradient of worst line) ÷ gradient of best line) x 100%
= %uncertainty
(worst line = shallowest or steepest line)
numerator of fraction = absolute uncertainty

Question 6

Write down everything you know about Micrometer screw gauge
(4)

Answer 6

Used for measuring small widths, thicknesses or diameters

Has a resolution of 0.01mm
Is made up of 2 scales

HOW TO READ:
1. Read the main scale first - each division = 0.5mm
2. Read the thimble scale - each division = 0.01mm —> read the number that aligns with the main scale and multiply it by 0.01
3. 1. + 2. = answer

Pros = better resolution
Cons = smaller measuring range, vernier callipers are quicker to use

Question 7

Write down everything you know about Vernier callipers
(3)

Answer 7

Used for measuring diameters and thicknesses, as well as the length of small distances such as a screw or the depth of a hole

Resolution = 0.1mm (however some are as small as 0.02-0.05mm)
Made up of 2 scales: the main scale and the vernier scale

HOW TO READ:
1. Read off the centimetre mark to the let of the vernier scale zero
2. Read off the millimeter mark to the left of the vernier scale zero
3. Find the point where the line matches up with the line on the bar scale. This tells you the number of tenths of a millimetre
4. Add the reading together to get your measurement (1. + 2. + 3. = answer)

Question 8

Write down everything you know about SI units
(3)

Answer 8

Base units:
Length (metre, m)
Mass (kilogram, kg)
Time (second, s)
Electric current (ampere, A)
Temperature (kelvin, K)
Amount of substance (mole, mol)
(+1 more)

Some derived units:
- area = m^2
- volume = m^3
- acceleration = ms^-2
- density = kgm^-3

Some derived units with special names:
- force (newton,N) = kgms^-2
- pressure (pascal,Pa) = Nm^-2
- energy or work done (Joule,J) = Nm
- power (Watt,W) = Js^-1
- electrical potential difference (Volt,V) = JC^-1
- electric resistance (ohm,Ω) = VA^-1
- electric charge (coulomb,C) = As
- frequency (hertz,Hz) = s^-1

Question 9

Write down everything you know about Scalar quantities
(2)

Answer 9

Scalar quantities have magnitude only

To add and subtract scalar quantities the quantities must have the same units
To multiply and divide scalar quantities the units can be the same or different but you must work out the final units correctly

Question 10

Write down everything you know about Vectors
(4)

Answer 10

Vector quantities have both magnitude and direction

COMBINING VECTORS
Parallel vectors - add together
Antiparallel vectors - make one +ve and the other -ve, then add them together
Two perpendicular vectors - top and tail, pythagoras for resultant force, tan for direction

RESOLVING VECTORS
- scale diagram
- trig

NON-PERPENDICULAR VECTORS
- scale diagram
- cosine and sine rules
- vector resolution