Answer
(a) $18\frac{m}{s}$
(b) Negative work
Work Step by Step
(a) We know that
$W=\Delta K.E$
$\implies mgh=\frac{1}{2}mv^2$
This simplifies to:
$v=\sqrt{2gh}$
We plug in the known values to obtain:
$v=\sqrt{2(9.81)(16)}$
$v=18\frac{m}{s}$
(b) The air resistance acted as an opposing force and reduced the speed and kinetic energy of the pine cone, so the air resistance did negative work.
