Question

Which one of the following SI base units is not matched to the correct unit of measurement?

A. Mass: kg
B. Time: s
C. Length: km
D. Temperature: K

Answer 1

The SI base unit incorrectly matched to its unit of measurement is C. Length: km. The correct SI base unit for length is the meter (m). Kilometers, milligrams, nanoseconds, and centiliters are metric units derived from the base units with the application of prefixes.

Step-by-step explanation:

The SI base unit that is not correctly matched to its unit of measurement among the options provided is C. Length: km (kilometer). The correct SI base unit for length is the meter (m), not kilometer (km). Kilometers, milligrams, nanoseconds, and centiliters are all derived units that use metric prefixes to scale the base units to larger or smaller sizes. These are particularly useful for a variety of applications, where measurements need to be expressed in more conveniently sized units than the base unit.

Here is the abbreviation for each unit mentioned in the question and its definition in terms of the base unit:

1. Kilometer (km) - 1 kilometer is equal to 1,000 meters (m).
2. Milligram (mg) - 1 milligram is equal to 0.000001 kilograms (kg) or 1/1,000,000 of a kilogram.
3. Nanosecond (ns) - 1 nanosecond is equal to 0.000000001 seconds (s) or 1/1,000,000,000 of a second.
4. Centiliter (cl) - 1 centiliter is equal to 0.01 liters (L) or 1/100 of a liter.

Answer 2

C. Length: km

Step-by-step explanation:

Let's analyze each option:

A. Mass: in the SI system, mass is measured in kilograms (kg), so this matching is correct.

B. Time: in the SI system, time is measured in seconds (s), so this matching is correct.

C. Length: in the SI system, length is measured in meters (m). The kilometer, instead, is a multiple of the meter (
`1 km = 1000 m`). Therefore, this matching is not correct.

D. Temperature: in the SI system, temperature is measured in Kelving (K), so this matching is correct.