Which statement correctly defines the unit of force, the newton?

• A. One newton is defined as 1 kg*m/s^2
• B. One newton is defined as 1 kg*m^2/s^2
• C. One newton is defined as 1 J
• D. One newton is defined as 1 kg*m/s

Answer: (A)

The key idea is that force is mass times acceleration. In SI units, this becomes newtons when you combine kilograms with meters per second squared: 1 N = 1 kg · m/s^2. So a force of 1 newton is the push that gives a 1-kilogram mass an acceleration of 1 meter per second per second. A handy check: a 1 kg mass at Earth's surface has weight about 9.8 N because W = m g ≈ 1 kg × 9.8 m/s^2. The other unit expressions describe different quantities: 1 kg·m^2/s^2 is a joule (energy), 1 J is the same energy unit, and 1 kg·m/s is momentum, not force.