
The bottom surface of the inverted conical vessel is parallel to the horizontal plane. The height of the cone is twice of the radius of the bottom. The container is partially filled with water. There is a small hole at the tip of the conical container. The speed of water leakage is 2cm^3/min. How long does it take for the water in the container to run out?
1: The water surface area is 9 π cm2
2: The distance between the water surface and the bottom of the container is 4 cm