A draft tube has the inlet diameter of 1 m and the outlet diameter of 2 m. The absolute pressure at the inlet of the draft tube is 0.4 bar. The outlet of the draft tube is exposed to atmosphere. The flow rate of water through the draft tube is 1600 litres per second. Then, the vertical distance between the inlet and the outlet is approximately ________.
1
0.06 m
2
6 m
3
60 m
4
0.6 m