The watt. This SI unit is named after James Watt. As for
all SI units whose names are derived from the proper name
of a person, the first letter of its symbol is uppercase (W). But
when an SI unit is spelled out, it should always be written in
lowercase (watt), with the exception of the “degree Celsius.”
from wikipedia
SI stands for Système Internationale. SI units are the ones that all engineers
should use, to avoid losing spacecraft.
SI units | ||
---|---|---|
energy | onejoule | 1 J |
power | one watt | 1 W |
force | one newton | 1 N |
length | one metre | 1 m |
time | one second | 1 s |
temperature | one kelvin | 1 K |
prefix | kilo | mega | giga | tera | peta | exa |
---|---|---|---|---|---|---|
symbol | k | M | G | T | P | E |
factor | 103 | 106 | 109 | 1012 | 1015 | 1018 |
prefix | centi | milli | micro | nano | pico | femto |
symbol | c | m | μ | n | p | f |
factor | 10-2 | 10-3 | 10-6 | 10-9 | 10-12 | 10-15 |
My preferred units, expressed in SI | |||
---|---|---|---|
energy | one kilowatt-hour | 1 kWh | 3 600 000 J |
power | one kilowatt-hour per day | 1 kWh/d | (1000/24) W ≅ 40 W |
force | one kilowatt-hour per 100 km | 1 kWh/100 km | 36 N |
time | one hour | 1 h | 3600 s |
one day | 1 d | 24 × 3600 s ≅ 105 s | |
one year | 1 y | 365.25 × 24 × 3600 s ≅ π × 107 s | |
force per mass | kilowatt-hour per ton-kilometre | 1 kWh/t-km | 3.6 m/s2 (≅ 0.37 g) |