How would the period of pendulum differ from an equivalent one on earth?
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If you know that that free fall acceleration g on the Moon is about 6 times less than on the Earth, it gives you the on the Moon the same pendulum will have a period about √6≈2.45 longer than on the Earth.

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.