Centripetal Force
M.12(1) - Centripetal Hoops
This apparatus can be used to demonstrate the flattening of the earth's poles. It consists of two spring metal rings (32 m in diameter for the large one and 10 cm in diameter for the small one) mounted at right angles to one another on a metal axis. The tops of the rings are free to slide along the center axis. The hoops is mounted in the mechanical rotator and set in motion slowly. As the speed is gradually increased, the loop will visibly flatten.
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M.12(2) - Rotator Globe
A glass sphere of about 15 cm in diameter has mercury and tinted pink water sealed in it. The sphere is set in motion slowly. As it rotates, the mercury distributes itself around the sphere's equator against the glass. The water also has the same distribution, but since it is less dense than mercury, it forms an internal layer. It will distribute itself against the mercury layer. Since there is more water than mercury in the sphere, a person standing away from the apparatus will see a central layer of mercury and two layers of pink water (top and bottom) while the sphere rotates.
This demonstrates that the centripetal force is greater for the more dense substance.
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M.12(3) -Loop-The-Loop
A ball rolling on this track demonstrates the relationship among potential, kinetic and rotational energies. Loop-the-loop is a circular section of track with rails of metal tubing held together by metal cross ties. It is attached to two straight sections of similar track. The ends of the cross ties have threads that fit short support rods for use in supporting the track. The apparatus is set with the circular section touching the floor, avoiding that a lot of the ball's energy being lost. Release the ball from one end of the track. The ball will orbit the track without losing contact and will reach the other end at the same height as it began. A ball rolling down a looped track will stay with the track, even at the top of the loop, if the speed at the top of the loop corresponds to the required centripetal force.
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