Answer
(a) $33.3N$
(b) double.
Work Step by Step
(a) We can find the required force as
$P=Fv$
This can be rearranged as:
$F=\frac{P}{v}$
We plug in the known values to obtain:
$F=\frac{50.0}{1.50}$
$F=33.3N$
(b) We know that $P=Fv$ or $v=\frac{P}{F}$. This equation shows that speed and power are directly proportional. Given that the power is doubled while the force remains constant, the speed of the Kayaker also becomes double.
