What is a derived unit?

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Preparation Staff asked 4 weeks ago

A derived unit is a unit of measurement that is derived from the combination of the seven base units of the SI system. Derived units are used to measure physical quantities that are not directly represented by a single base unit but rather by a relationship between base units.

The concept of derived units is central to the SI system because many physical quantities cannot be adequately described by a single base unit. For example, quantities such as speed, acceleration, force, and energy require combinations of different base units to describe them fully.

A derived unit can be formed by multiplying or dividing the base units. For example:

  1. Speed: Speed is defined as the rate at which an object moves. It is derived from the fundamental quantities of length (meter, m) and time (second, s). The unit of speed is meters per second (m/s), representing the distance traveled per unit of time.

  2. Acceleration: Acceleration is the rate of change of velocity with respect to time. It is derived from the base units of length and time. The unit of acceleration is meters per second squared (m/s²), which indicates how much the velocity of an object changes each second.

  3. Force: Force is derived from the fundamental quantities of mass (kilogram, kg), length (meter, m), and time (second, s). The unit of force is the newton (N), and it is defined as 1 kg·m/s². This means that one newton is the force required to accelerate a 1-kilogram mass by 1 meter per second squared.

  4. Pressure: Pressure is defined as force per unit area. It is derived from the base units of mass, length, and time. The unit of pressure is the pascal (Pa), defined as 1 N/m², which means 1 newton per square meter.

Derived units are essential because they allow scientists and engineers to describe a wide variety of physical phenomena. By using combinations of the base units, we can describe almost any physical property, from the energy contained in a system to the momentum of an object.

These derived units are consistent and can be universally understood, which is crucial for communication in scientific and engineering fields. The SI system ensures that all derived units are based on the same set of fundamental principles, promoting standardization across disciplines.