A man leans over the edge of a cliff and throws a rock upward at 4.9 m/s. Neglecting air resistance, two seconds later the rock's speed is what?

Answer 1

Subtract g*t = 19.6 m/s^2 from +4.9 m/s.
The speed will be downward at that time.

Speed is a magnitude, and is always considered positive. So the answer is 14.7 m/s