What is the frquency of vibration if the balance wheel of a wrist watch makes 90 revolutions in 25 s?

Answer Details

The frequency of vibration can be calculated using the formula:
frequency = number of revolutions/time taken
In this case, the balance wheel of a wrist watch makes 90 revolutions in 25 seconds. So, the frequency can be calculated as:
frequency = 90/25
frequency = 3.6 Hz
Therefore, the frequency of vibration is 3.6 Hz. Option D, "3.60 Hz", is the correct answer.