Various objects are raced down an inclined plane. There are two sets of disks, one with the mass distribution concealed and the other with the mass distribution apparent. All of the three inch disks have the same mass which you can demonstrate by placing two at a time on a double pan balance. There are also a few smaller disks available so you can demonstrate that disks of the same mass distribution but different sizes and masses roll the same.
Unidentified Rolling Objects (Audience Appeal)
These demonstrations are often shown with the rolling objects above,
or on the first day of class, or at physics demonstration shows, to
attract interest in physics, and as an illustration scientific reasoning
in working out their mechanism "How would you design a mechanical
system to do this?"
One of the "unpredictable disks", shown above, rolls down and one rolls up. The off-center weight is concealed from the audience, but can be shown after they have tried to reason out the mechanism. A "prematurely-stopping cylinder" rolls part way down and stops. A "come-back disk" rolls down some distance, and then rolls back up!
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