Straight up is only vertical direction. If we say up is positive, there will be -9.8m/s^2 gravitational acceleration downward. When the rock reaches its highest point, velocity will be zero, it then starts to fall back down with negative velocity.
use this kinematic equation: v = u + at , because it has all the given or required variables.
0 = 14.2 - 9.8t
9.8t = 14.2
t = 14.2/9.8
t = 1.45 seconds
* this is assuming speed of 14.2 is in m/s
