Answer:
[tex]a_y=0.92m/s^2[/tex]
Explanation:
To solve this problem we use the formula for accelerated motion:
[tex]y=y_0+v_{y0}t+\frac{a_yt^2}{2}[/tex]
We will take the initial position as our reference ([tex]y_0=0m[/tex]) and the downward direction as positive. Since the rock departs from rest we have:
[tex]y=\frac{a_yt^2}{2}[/tex]
Which means our acceleration would be:
[tex]a_y=\frac{2y}{t^2}[/tex]
Using our values:
[tex]a_y=\frac{2(0.86m)}{(1.37s)^2}=0.92m/s^2[/tex]