WHICH IS NOT a correct SI unit?
1- ms^-1
2-kg
3-g
4- kmh^-2 and why
To determine which option is not a correct SI unit, we need to understand the SI unit system and its conventions.
The International System of Units (SI) is a widely used system for measuring quantities in scientific and everyday contexts. It is based on seven base units, from which all other units are derived.
1. ms^-1: This unit represents meters per second, which is the SI unit for velocity or speed. It is correct because it follows the SI convention of combining a base unit (meter) with a prefix (milli-) and an exponent (-1) for the inverse.
2. kg: This unit represents kilograms, which is the SI unit for mass. It is correct because it is one of the seven base units of the SI system.
3. g: This unit represents grams, which is not a base unit in the SI system. However, it is a derived unit that is commonly used when dealing with small masses. It is also an acceptable unit within the SI system, but it may be preferable to use kilograms for larger masses.
4. kmh^-2: This unit represents kilometers per square hour, which is not a correct SI unit. The SI unit for speed or velocity is meters per second (m/s), not kilometers per hour (km/h). Additionally, the exponent of -2 for the square hour is not a valid SI convention for this context.
Therefore, the correct answer is option 4 - kmh^-2 because it does not represent a valid SI unit.