Glass in free fall

Question a)

Data

H = 1.5 m
When it gets to the ground y = 0 m.
g = 10 m/s²

Resolution

To answer this question simply apply the position equation in free fall and solve for time when the glass is at y = 0 m, that is, when it reaches the ground:

$$\begin{gathered} y=H-\frac{g·t^2}{2}\Rightarrow \\ t=\sqrt{\frac{-2·(y-H)}{g}}\Rightarrow \\ t=\sqrt{\frac{-2·(0-1.5)}{10}}\Rightarrow \\ t=\sqrt{\frac{3}{10}}\Rightarrow \\ \boxed{t=0.55} \end{gathered}$$

Question b)

Data

H = 1.5 m
When it gets to the ground y = 0 m.
g = 10 m/s²
Time that it takes to reach the ground t = 0.55 s

Resolution

Since we know the time that it takes reaching the floor, it is enough to apply the equation of velocity for that time:

$$\begin{gathered} v=-g·t \Rightarrow \\ v = -10 m/s^{\cancel{2}}·0.55 \cancel{s }\Rightarrow \\ \boxed{v = 5.5 m/s} \end{gathered}$$