Because if we hang the metal tape down, it means that the wheel has 1 revolution, so if we take the metal tape on a table it would have good condition before you do the experiment.
If we hang a metal tape down, it means that the wheel rotates one revolution, so if we put on the table, metal tape is in good condition before the experiment.
Because if we hang metal tape down means spinning wheel 1 revolution, so if we take the tape on the table, it will be a good condition of metal before experiment .