Newton's Second Law of Motion
Newton's Second Law states that the force on an object equals its mass times its acceleration: F = m × a. This force calculator solves for force, mass or acceleration when you enter the other two. It supports newtons and pound-force, kilograms, grams and pounds, and accelerations in m/s² or in g (standard gravity). It also shows the weight equivalent and g-force.
Force Formulas
Example: accelerating a 1,200 kg car at 3 m/s² requires 1,200 × 3 = 3,600 N of force. That acceleration is about 0.31 g.
- Force: F = m × a
- Mass: m = F ÷ a
- Acceleration: a = F ÷ m
- 1 newton (N) = 1 kg × 1 m/s². 1 g = 9.80665 m/s².
Weight Is a Force
Your weight is the force of gravity on your mass: W = m × g. A 70 kg person weighs 70 × 9.81 ≈ 687 N on Earth. On the Moon, where gravity is about one-sixth as strong, the same person would weigh only about 114 N, even though their mass is unchanged.
Frequently Asked Questions
What is the difference between mass and weight?
Mass is the amount of matter in an object and stays the same everywhere. Weight is the force gravity exerts on that mass, so it changes depending on where you are.
What does g-force mean?
g-force expresses acceleration as a multiple of Earth's gravity. 1 g is normal standing, a fast roller coaster might reach 4–5 g, and fighter pilots can experience 9 g in tight turns.
How do I convert newtons to pound-force?
Divide by 4.448. One pound-force (lbf) equals about 4.448 newtons, so 100 N ≈ 22.5 lbf.