Cross section of a stream flowing from a hole

[rbwang1225]

Homework Statement

Consider a cylindrical tank filled with water with 2.5-m depth. The water emerges from a small hole at the center of the bottom, as shown in the figure. The diameter of the hole is 1 mm. The cross-section area of the vertical water stream decreases as it falls. Find the diameter of the water stream at the position 7.5 m from the hole.

Homework Equations

I think I have to address the continuity equation $v_{1}a_2=v_2a_2$, but I don't know how to start.

Any help would be appreciated.

 

[LawrenceC]

Hint: After the stream leaves the tank, does its velocity remain constant?