Answer
a) 34.6 m/s
b) 14.4 m/s
Work Step by Step
Let down be the negative direction
a)
$v=u+at$
$u=v-at$
$u=(15)-(-9.8)(2.0)=34.6\; m/s$
b)
$v=u+at$
$v=(34.6)+(-9.8)(5.0)=-14.4\; m/s$
OR, without using the answer from part a
$v=u+at$
$v=(15)+(-9.8)(5.0-2.0)=-14.4\; m/s$
Hence, the speed is 14.4 m/s.
