Units & conversions — Hyunjoo Park

Not on the formula sheet.

Power vs energy

$W$ is rate (power), $Wh$ is amount (energy). $1\ \text{W} = 1\ \text{J/s} \qquad 1\ \text{kWh} = 3.6\ \text{MJ}$

Unit	Quantity	From	=
N	force	$F = ma$	$\text{kg·m/s}^2$
Pa	pressure	$p = F/A$	$\text{N/m}^2 = \text{kg/(m·s}^2)$
J	energy	$E = F \cdot d$	$\text{N·m}$
W	power	$P = E/t = F \cdot v$	$\text{J/s}$

$1\ \text{ktoe} \approx 11.6\ \text{GWh} \approx 42\ \text{TJ}$ (1 tonne of oil ≈ 12 MWh); usually given in the exam, check for typos
World average energy use ≈ 65 kWh/(person·day) (2018, Introduction lecture; 1998: 53) → benchmark for “compare to the global average” (not given in the exam)
$1\ \text{ppm} = 1000\ \text{ppb}$
$1\ \text{m}^3 = 1000\ \text{L}$
$T[\text{K}] = T[°\text{C}] + 273$ ; a difference $\Delta T$ is the same in °C and K

Unit check (atmosphere mass, HW 1A)

$M = \frac{pA}{g} \rightarrow \frac{\text{kg/(m·s}^2)\cdot\text{m}^2}{\text{m/s}^2} = \text{kg}$ ✓