Which one of the following quantities has a correct unit? | Quantity | Unit | |---|---| | A speed | km⋅h⁻¹ | | B wavelength | Hz | | C mechanical energy | J⋅s⁻¹ | | D resistance | A |
Answer (1)
To determine which of the given options has the correct unit, let's review each quantity with its appropriate unit:
Speed : Speed is the rate at which an object moves. Its unit in the metric system is typically meters per second (m/s), but kilometers per hour (km/h) is also a valid unit, commonly used for everyday purposes like measuring the speed of vehicles. Therefore, the unit km⋅h⁻¹ is correct for speed.
Wavelength : Wavelength is the distance between consecutive peaks of a wave. Its unit is generally meters (m) or nanometers (nm), not Hz. Hertz (Hz) is a unit of frequency, which is inversely related to wavelength.
Mechanical Energy : Mechanical energy is the sum of potential and kinetic energy in a system. The standard unit of energy in the metric system is the joule (J). J⋅s⁻¹, however, represents power (or energy per unit time), not energy itself.
Resistance : Resistance in electrical circuits is the measure of the opposition to current flow. Its unit is the ohm (Ω), not ampere (A). Ampere is the unit of electric current.
Based on the above explanations, the correct unit is given in option A: Speed with the unit km⋅h⁻¹.
