## Precalculus (6th Edition) Blitzer

$32$, $upward$
Velocity is the derivative of distance (height in this case). From the given derivative $s'(a)=-32a+64$, at $a=1$, we have the velocity $s'(1)=-32+64=32$ feet per second. The positive sign indicates that the ball is moving $upward$ when $t=1$ second.