Problem $6($Bonus $+1$ p$)$:

Derive the expression for the velocity $v=r^{}$ of the

particle P in the spherical coordinate system. Start

from the position vector $r=r{u}_r.$

Spherical coordinates $r=r(t),=(t)$ and $=(t)$

are defined as: $r$ distance from the origin, $$ angle from

$z-$axis, $$ rotation about $z-$axis.