442hz the should be the correct answer
Friction made it difficult because an object in motion may not always stay in motion due to the friction caused by its movement. For instance, if you roll a ball down a straight platform, it will not go on forever. The friction of the platform and the ball with eventually slow it down and stop it.
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1/20.... Frequency and period are inverses so whatever frequency is, period is one over that number. And versa visa
Answer: Gravitational force between the two masses does not depend on the medium separating two masses.