https://joy.videvo.net/videvo_files/video/free/2019-02/large_watermarked/181004_01_4K-Science_13_preview.mp4 Balls Rolling Down Channels in Laboratory Metal balls dropping into different types of liquid. analysisballballschemistchemistrydiscoveryequipmentexperimentgravitylablaboratoryresearchrollingsciencescientifictesttestingviscosity