1. Metric Units

2. Starter

3. Metric Units Why is a metre the length it is?
All metric units were chosen based on concepts which will not change (unlike Imperial Units)
A metre is:
‘The distance travelled by light in a vacuum in 1/299,782,458 of a second’
The awkward number was chosen as it made it easier for scientists to calculate the wavelength of laser beams…
A vacuum is the name given by scientists to a space where there is nothing at all!

4. Metric Units Why is a second the length of time it is?
All metric units were chosen based on concepts which will not change (unlike Imperial Units)
A second is:
‘the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom’
To summarise, a second is how long it takes an atom to release a certain amount of radiation!

5. The international prototype kilogram
Metric Units
Why is a kilogram the weight it is?
All metric units were chosen based on concepts which will not change (unlike Imperial Units)
A kilogram is measured by the International Prototype Kilogram:
The international prototype kilogram
 There are many copies in the world as over time, these decay and lose weight.. (hardly noticable though)

6. Metric Units Metric Conversions
 You need to be able to convert between metric units
x 1000
x 100
x 10
Kilometre
Metre
Centimetre
Millimetre 1
1000 1
100 1 10
÷ 1000
÷ 100
÷ 10
a) Convert 5.6km into metres
 5.6 x 1000
= 5600m
b) Convert 32,000mm into metres
 32,000 ÷ 10
= 3,200cm
 3,200 ÷ 100
= 32m

7. Metric Units Metric Conversions
 You need to be able to convert between metric units
x 1000
x 1000
Tonne
Kilogram
Gram 1
1000 1
1000
÷ 1000
÷ 1000
a) Convert 8.12 Tonnes into kilograms
 8.12 x 1000
= 8120kg
b) Convert 16,500g into Tonnes
 16,500 ÷ 1000
= 16.5kg
 16.5 ÷ 1000
= t

8. Metric Units Metric Conversions
 You need to be able to convert between metric units
x 1000
Litre
Millilitre 1
1000
÷ 1000
a) Convert 7.1 Litres into Millilitres
 7.1 x 1000
= 7100ml
b) Convert 25 Millilitres into Litres
 25 ÷ 1000
= 0.025L

9. Metric Units “Kilo” means 1000  eg) Kilometre = 1000 metres
 eg) Kilogram = 1000 grams
“Milli” means 1/1000
 eg) Millimetre = 1/1000 of a metre
 eg) Milligram = 1/1000 of a gram

10. Metric Units kilo (km) 1,000m Mega (Mm) 1,000,000m
Giga (Gm) 1,000,000,000m
Tera (Tm) 1012m
Peta (Pm) 1015m
Exa (Em) 1018m
Zetta (Zm) 1021m
Yotta (Ym) 1024m

11. Metric Units milli (mm) 0.001m micro (μm) 0.000001m
nano (nm) m
pico (pm) m
femto (fm) m
atto (am) m
Zepto (zm) m
Yocto (ym) m

12. Metric Units
The previous ‘prefixes’ will most likely be seen in computing
Bytes  Kilobytes
Kilobytes  Megabytes
Megabytes  Gigabytes
Gigabytes  Terabytes??