Here's why:

* Newton's Second Law: Force is defined as mass times acceleration (F = ma).

* SI Units: The standard unit of mass is the kilogram (kg) and the standard unit of acceleration is meters per second squared (m/s²).

* Derived Unit: Combining these units gives us the newton (N) as the derived unit of force: 1 N = 1 kg * m/s².

So, a force of one newton is the force required to accelerate a mass of one kilogram at a rate of one meter per second squared.