Newton Definition

The unit of force called the newton is named in honor of Sir Isaac Newton, who experienced force firsthand when an apple fell on his head.
Enoch Seeman, Getty Images

A newton is the SI unit of force. It is named in honor of Sir Isaac Newton, the English mathematician and physicist who developed laws of classical mechanics.

The symbol for newton is N. A capital letter is used because the newton is named for a person (a convention used for symbols of all units).

Formulas and Examples 

One newton is equal to the amount of force needed to accelerate a 1 kg mass 1 m/sec2. This makes the newton a derived unit because its definition is based on other units.
1 N = 1 kg·m/s2

The newton comes from Newton's second law of motion, which states:

F = ma

where F is force, m is mass, and a is acceleration. Using the SI units for force, mass, and acceleration, the units of the second law become:

1 N = 1 kg⋅m/s2

A newton is not a large amount of force, so it is common to see the kilonewton unit, kN, where:

1 kN = 1000 N

Newton Examples

The gravitational force on Earth is, on average, 9.806 m/s2. In other words, a kilogram mass exerts about 9.8 newtons of force. To put that in perspective, about half of one of Isaac Newton's apples would exert 1 N of force.

The average human adult exerts about 550-800 N of force, based on an average mass ranging from 57.7 kg to 80.7 kg.

The thrust of an F100 fighter jet is approximately 130 kN.