See the guide for this topic.
1.1 – Measurements in physics

Fundamental and derived units
Fundamental SI units
Quantity  SI unit  Symbol 
Mass  Kilogram  kg 
Distance  Meter  m 
Time  Second  s 
Electric current  Ampere  A 
Amount of substance  Mole  mol 
Temperature  Kelvin  K 
Derived units are combinations of fundamental units. Some examples are:
 m/s (Unit for velocity)
 N (kg*m/s^^{2)} (Unit for force)
 J (kg*m^2/s^2) (Unit for energy)

Scientific notation and metric multipliers
In scientific notation, values are written in the form a*10^n, where a is a number within 1 and 10 and n is any integer. Some examples are:
 The speed of light is 300000000 (m/s). In scientific notation, this is expressed as 3*10^8
 A centimeter (cm) is 1/100 of a meter (m). In scientific notation, one cm is expressed as 1*10^2 m.
Metric multipliers
Prefix  Abbreviation  Value 
peta  P  10^15 
tera  T  10^12 
giga  G  10^9 
mega  M  10^6 
kilo  k  10^3 
hecto  h  10^2 
deca  da  10^1 
deci  d  10^1 
centi  c  10^2 
milli  m  10^3 
micro  μ  10^6 
nano  n  10^9 
pico  p  10^12 
femto  f  10^15 

Significant figures
For a certain value, all figures are significant, except:
 Leading zeros
 Trailing zeros if this value does not have a decimal point, for example:
 12300 has 3 significant figures. The two trailing zeros are not significant.
 012300 has 5 significant figures. The two leading zeros are not significant. The two trailing zeros are significant.
When multiplying or dividing numbers, the number of significant figures of the result value should not exceed the least precise value of the calculation.
The number of significant figures in any answer should be consistent with the number of significant figures of the given data in the question.
FYI
 In multiplication/division, give the answer to the lowest significant figure (S.F.).
 In addition/subtraction, give the answer to the lowest decimal place (D.P.).

Orders of magnitude
Orders of magnitude are given in powers of 10, likewise those given in the scientific notation section previously.
Orders of magnitude are used to compare the size of physical data.
Distance  Magnitude (m)  Order of magnitude 
Diameter of the observable universe  10^26  26 
Diameter of the Milky Way galaxy  10^21  21 
Diameter of the Solar System  10^13  13 
Distance to the Sun  10^11  11 
Radius of the Earth  10^7  7 
Diameter of a hydrogen atom  10^10  10 
Diameter of a nucleus  10^15  15 
Diameter of a proton  10^15  15 
Mass  Magnitude (kg)  Order of magnitude 
The universe  10^53  53 
The Milky Way galaxy  10^41  41 
The Sun  10^30  30 
The Earth  10^24  24 
A hydrogen atom  10^27  27 
An electron  10^30  30 
Time  Magnitude (s)  Order of magnitude 
Age of the universe  10^17  17 
One year  10^7  7 
One day  10^5  5 
An hour  10^3  3 
Period of heartheart  10^0  0 

Estimation
Estimations are usually made to the nearest power of 10. Some examples are given in the tables in the orders of magnitude section.
1.2 – Uncertainties and errors

Random and systematic errors
Random error  Systematic error 
Caused by fluctuations in measurements centered around the true value.
Can be reduced by averaging over repeated measurements. 
Caused by fixed shifts in measurements away from the true value.
Cannot be reduced by averaging over repeated measurements. 
Examples:
Fluctuations in room temperature The noise in circuits Human error 
Examples:
Equipment calibration error such as the zero offset error Incorrect method of measurement 

Absolute, fractional and percentage uncertainties
Physical measurements are sometimes expressed in the form x±Δx. For example, 10±1 would mean a range from 9 to 11 for the measurement.
Absolute uncertainty  Δx 
Fractional uncertainty  Δx /x 
Percentage uncertainty  Δx/x*100% 
Calculating with uncertainties
Addition/Subtraction  y=a±b  Δy=Δa+Δb (sum of absolute uncertainties) 
Multiplication/Division  y=a*b or y=a/b  Δy/y=Δa/a+Δb/b (sum of fractional uncertainties) 
Power  y=a^n  Δy/y=nΔa/a (n times fractional uncertainty) 

Error bars
Error bars are bars on graphs which indicate uncertainties. They can be horizontal or vertical with the total length of two absolute uncertainties.

Uncertainty of gradient and intercepts
Line of best fit: The straight line drawn on a graph so that the average distance between the data points and the line is minimized.
Maximum/Minimum line: The two lines with maximum possible slope and minimum possible slope given that they both pass through all the error bars.
The uncertainty in the intercepts of a straight line graph: The difference between the intercepts of the line of best fit and the maximum/minimum line.
The uncertainty in the gradient: The difference between the gradients of the line of best fit and the maximum/minimum line.
1.3 – Vectors and scalars

Vector and scalar quantities
Scalar  Vector 
A quantity which is defined by its magnitude only.  A quantity which is defined by both is magnitude and direction. 
Examples:
Distance Speed Time Energy 
Examples:
Displacement Velocity Acceleration Force 

Combination and resolution of vectors
Vector addition and subtraction can be done by the parallelogram method or the head to tail method.
When resolving vectors in two directions, vectors can be resolved into a pair of perpendicular components.
FYI
The relationship between two sets of data can be determined graphically.
Relationship  Type of Graph  Slope  yintercept 
y=mx+c  y against x  m  c 
y=kx^n  logy against logx  n  logk 
y=kx^n+c with n given  y against x^n  k  c 