1. 1.1. Measurements in physics
SI system: an international agreement on standard units
Based on 7 basic units:
(180917)
Quantity
Unit
Length s
meter m
Time t
second
Mass
kilogram* kg
Electric current I
Ampere A
Temperature T
Kelvin K
Ammount of substance n
mole
mol
Luminous intensity
candela cd
∗the only basic SI unit with a prefix
All other are derived units (combinations of the basic units)
Quantity
Unit
Velocity v
Meters per second
m s-1
Force F
Newton (= kilogram meters per second squared)
N (= kg m s-2)

2. We often need to convert between SI-units and other units
Ex. 1: a) how many meters are 2 ft? b) how many feet are 2 meters? (1 ft = m)
Ex. 2: How many km/h is 45 mph? (1 mile = 1609 m)

3. When dealing with large or small numbers we can use
Prefixes (metric multipliers)
Powers of ten (scientific notation)
Ex. 3: Write m
a) with a prefix
b) in sci. not.

4. Rounding:
Never round before you get your final answer!
Always round your final answer!
Round according to weakest link of input
Mult/div: number of significant figures
(Add/sub: least number of decimal places)
(Final number 5 rounded up if number before is odd)
3.55 ≈ 3.6, 3.65 ≈ 3.6
Order of magnitude estimation: round to nearest power of ten for quick calculations
Ex: How many times will your heart beat?