Quick answer
This calculator uses Newton’s second law, F = ma, to find force, mass or acceleration. Choose the quantity you want, enter the other two, and the calculator shows the answer with the formula and substitution.
F = ma calculator
How to Use the F = ma Calculator
- Choose whether you want force, mass or acceleration.
- Enter the two known values in SI units: newtons, kilograms and m/s².
- Press Calculate to get the result and the working.
Tip: Use the net force: add all the forces on the object as vectors first, then use F = ma.
Newton’s Second Law Formula
F = ma
F is the net force in newtons (N), m is the mass in kilograms (kg) and a is the acceleration in m/s². Rearranged: m = F ÷ a and a = F ÷ m.
One newton is the force needed to accelerate a 1 kg mass at 1 m/s². Our full guide to Newton’s second law explains the law in depth with free-body diagrams.
Worked Example
Worked example: pushing a trolley
Question: A shopping trolley of mass 25 kg accelerates at 0.8 m/s². What net force acts on it?
- Choose “Net force (F)”.
- F = m × a = 25 × 0.8.
- F = 20 N.
Answer: The net force is 20 N in the direction of the acceleration.
Common Mistakes
- Using weight in newtons as if it were mass in kilograms. Mass = weight ÷ g.
- Forgetting to subtract opposing forces like friction before using F = ma.
- Entering grams instead of kilograms: 500 g is 0.5 kg.
Practise: work through these Newton’s second law MCQs with worked answers.
Use this Newton’s second law calculator to check force, mass and acceleration problems quickly. The Newton’s second law calculator always shows the rearranged formula, so you can learn the method as well as the answer.
Frequently Asked Questions
What is Newton’s second law?
Newton’s second law states that the net force on an object equals its mass multiplied by its acceleration, F = ma. A larger force gives a larger acceleration; a larger mass gives a smaller one.
What are the units of force?
Force is measured in newtons (N). 1 N = 1 kg·m/s².
Can acceleration be negative in F = ma?
Yes. A negative result means the net force and acceleration point in the negative direction, for example when an object is slowing down.