Sam threw a stone horizontally at a speed of 5m/s from a 9.8 m tall building. how much time does the stone take to hit the ground?

The given is a projectile motion with angle equal to 90° at which the motion would become horizontal. The projectile motion has two components for the distance. The horizontal component would progress at a constant rate each second while the vertical component would become greater as time progress. 

In this item, we are asked to determine the amount of time that would be needed for the stone to hit the ground. This can be calculated through the equation,
            
           d = V₀t + (1/2)(gt²)
It is to be noted that V₀ has a y-component equal to zero. 

Substituting this value to the equation,
          9.8 m = (0) + (1/2)(9.8 m/s²)(t²)
                  t = sqrt (2) = 1.41 s

Hence, the time would be equal to 1.41 s.