Low-cost experiment to determine the shape of the surface of a rotating liquid using the smartphone

In this work, we investigate a low-cost experiment to explore physics when a “leaf of water” is in rotation, under the action of weight and normal forces. A portion of water with red food coloring was placed in a container that we built with transparent acrylic in the shape of a cobblestone, this container was attached to a fidget spinner that allows the system to rotate around its vertical axis. We studied the physics involved in this problem and we calculated the theoretical curve that describes the behavior of the water in rotation. We verify that the curve depends on the width of the container and the angular velocity. We use the free Phyphox app to take angular velocity measurements and we can compare the theoretical curve with the experimental curve. To make this comparison, we made an applet in the GeoGebra software that made it possible to compare the theory with a photo of the experience.

Keywords
Teaching physics; rotating liquid; low cost experiment; smartphone