\magnification=\magstep2


$$
\thinspace { {d \vec{p}}\over{dt} } \thinspace  
            = \thinspace  {{{ d{(m \vec{v})} }\over{dt} }}
            = \thinspace  {m  {{ d\vec{v}}\over{dt} }}
$$

$$
\thinspace { {d \vec{p}}\over{dt} } \thinspace  
            = \thinspace  {{{ d{(m \vec{v})} }\over{dt} }}
            = \thinspace  {m  {{ d\vec{v}}\over{dt} }} + 
                     { \vec{v} { {(dm)} \over {dt}} }
$$


\bye
