Equipment for demonstrating Newton's third law and the energy conservation law in mechanics have successfully been constructed utilizing fine spherical plastic beads in place of metal ball bearings. To demonstrate Newton's third law, special magnetized Petri dishes were employed as objects, while to examine the energy conservation law, a large-angle frictionless slope (θ = 50°) consisting of a thin plastic sheet on which the fine plastic beads were attached by the electrostatic force was employed. Using this method, a quantitative measurement of the energy conservation law was successfully carried out with a small error of less than 3%. A great advantage of this frictionless method is that we can use the same object (a Petri dish) to demonstrate many kinds of mechanics laws, such as the first, second and third laws of motion, the momentum conservation law, and the energy conservation law.
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