Final answer:
A derived unit in physics is formed by combining base units or a base unit with a numerical prefix. It is obtained by using mathematical operations on the base units.
Step-by-step explanation:
A derived unit in physics is a unit that is formed by combining different base units or a base unit with a numerical prefix. It is obtained by using mathematical operations such as multiplication or division on the base units. For example, the unit of area is square meters (m2), which is derived by multiplying the length unit (meter) by itself. Similarly, the unit of speed is meters per second (m/s), which is derived by dividing the length unit by the time unit.