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名晃 發問於 社會及文化語言 · 9 年前

come back can

I want to ask that :What is the 3Cs of come back can ??


a)Variable to be changed

b)Variables to be kept constant

c)Result to be compared

Thanks a lot!!

p.s If you have any more information about come back can,you can give it to me.THANKS SO MUCH!!

1 個解答

  • 匿名
    9 年前

    3C's of Come Back Can

    a). Variable to be changed - the weight with hole through its centreb) Variables to be kept constant - the same rubber band, the same can,the same number of rotations of the canc) Result to be compared - the distance the can rolls before it stops



    Come-back Can

    A can, when rolled across a table, comes to rest and then rolls back to where it started, illustrating the concept of stored internal energy.


    cylindrical can with removable, opaque lid

    rubber band

    weight with hole though its centre


    A can is constructed with a rubber band strung between the center of its ends and a weight connected to the band so as to cause the band to wind up as the can rolls. The can comes to rest and then rolls back to where it started. The appearance is that the table is not level, but it can be rolled in either direction with the same result. It helps to rotate the can a turn or two before releasing it to compensate for the frictional losses as it rolls. This also allows the can to roll up a slight incline. One end of the can should be easily removable to reveal its contents and to explain its operation.


    This demonstration illustrates the conversion of kinetic to potential energy and back. The potential energy is stored internally in the twisted rubber band. On the microscopic level, the energy is stored in the electric potential of the charged particles that make up the molecules of the rubber. Analogies can be made to winding a watch, to filling an automobile gasoline tank, to the stored energy in atoms and molecules and the energy of mass itself (E = mc^2).

    From the standpoint,,,(see reference below)

    How to make one.: