In the SI system, frequency is measured in which unit?

• A. Newton (N), equivalent to $kg·m·s^{\mathrm{-2}}$
• B. Hertz (Hz), equivalent to $s^{\mathrm{-1}}$
• C. Joule (J), equivalent to $kg·m^2·s^{\mathrm{-2}}$
• D. Watt (W), equivalent to $kg·m^2·s^{\mathrm{-3}}$

Answer: (B)

Verified step by step guidance

1. Understand that frequency is defined as the number of occurrences of a repeating event per unit time.
2. Recall that the SI unit of time is the second (s), so frequency must be expressed in terms of inverse seconds.
3. Recognize that the unit Hertz (Hz) is defined as one cycle per second, which can be written as \(\text{Hz} = \text{s}^{-1}\).
4. Compare this with other units given: Newton (N) is \(\text{kg} \cdot \text{m} \cdot \text{s}^{-2}\), Joule (J) is \(\text{kg} \cdot \text{m}^2 \cdot \text{s}^{-2}\), and Watt (W) is \(\text{kg} \cdot \text{m}^2 \cdot \text{s}^{-3}\), none of which represent frequency.
5. Conclude that the correct SI unit for frequency is Hertz (Hz), equivalent to \(\text{s}^{-1}\).