PX155 - E7 - back to levers

lever balances if $\frac{d \vec{L}}{d t} = 0$
ie: total $\vec{τ}$ about $P = 0$
zero torque if $r_{1} W_{1} = r_{2} W_{2}$ as per archimedes'
conclusion: archimedes' lever equation is contained within A - foundations of classical mechanics
torque:

\vec{τ} = \vec{r} \times \vec{F}

\vec{L} = \vec{r} \times \vec{p}

\1\n\2\n