If you rotate the water tank you can observe how the water surface forms a curve. The higher the rotation, the more the water surface bends. When the water tank is stationary, only gravity acts on the water particles, resulting in a horizontal water surface. However, if the water tank is rotated, the centrifugal force also acts on the water particles, which increases with the distance from the axis of rotation. This causes a rise in the water level at the sides and the formation of a parabolic shape.