How it works
Newton's second law states that force equals mass times acceleration — the relationship between the force applied to an object, its mass, and the acceleration it experiences. Rearrange the formula and you can solve for any one of the three if you know the other two.
F = m × a
m = F ÷ a
a = F ÷ m
Force is measured in newtons (N), mass in kilograms (kg), and acceleration in metres per second squared (m/s²). A negative acceleration represents deceleration — slowing down or a force in the opposite direction to motion.
Worked example
A 10 kg object accelerating at 5 m/s².
- Use the formula F = m × a.
- Substitute: F = 10 × 5.
- That gives 50 newtons.
The force required is 50 N.
Common questions
What is Newton's second law?
It states that force equals mass times acceleration (F = ma) — the more mass an object has, or the faster it accelerates, the more force is required to produce that acceleration.
What units does this use?
SI units throughout: newtons for force, kilograms for mass, metres per second squared for acceleration. To convert pounds-force or slugs, convert before entering values here.
Can acceleration be negative?
Yes — a negative value represents deceleration (slowing down) or a force acting in the opposite direction to motion. Enter it as a negative number and the calculator handles the sign correctly.