AThe final velocity is
\(12\ m/s\ up+4\ m/s^{2}\ down*3\ s\)
\(=12\ m/s-4\ m/s^{2}*3\ s\)
\(=12\ m/s-12\ m/s\)
\(=0\)
So the elevator has final velocity 0 (and no direction).
(B) The distance moved is
\(d=v_{i}t+\frac{1}{2}at^{2}\)
where \(v_{i}=\) the initial velocity, \(a=\) acceleration, and \(t=\) time.
So we get
\(d=12\ m/s*3\ s-\frac{1}{2}(4\ m/s^{2})(3\ s)^{2}\)
\(=36-2*9\)
\(=36-18\)
\(=18\ m\)
so the elevator moved 18 meters upwards.
