The spill-not is a piece of equipment that can be used in the classroom to explain the forces of science. The spill-not is swung around with a cup of water on it, as shown in the video. The cup of water follows the rules of inertia, an object in motion stays in a straight path until acted on by an unbalanced force. The water stays in a straight path as it is swung and once it flips over, the bottom of the spill-not acts as an unbalanced force as it pushes the cup up and over, breaking its straight path.