Force Calculator (F = ma)

The SI unit of force is the Newton (N), defined as 1 kg × 1 m/s² = 1 N. One Newton is approximately the force needed to hold a 100 g apple against gravity. The weight of a 1 kg object at Earth's surface is approximately 9.81 N (1 kg × 9.81 m/s² gravity).

Mass is the amount of matter in an object (measured in kg) and does not change with location. Weight is the gravitational force on that mass (measured in Newtons): W = mg where g = 9.81 m/s². A person with 70 kg mass weighs 70 × 9.81 = 686.7 N on Earth, but only 113 N on the Moon.

Rocket thrust produces a force that accelerates the rocket. As fuel burns off, mass decreases, so the same thrust produces increasing acceleration (a = F/m). This is why rockets accelerate faster as they burn fuel. The opposite — greater mass needing more force — is why fuel efficiency in heavy vehicles is so challenging.