Using the model
Symbols, assumptions and limitations
The force entered is the net external force along one chosen axis. Mass must be positive; force and acceleration may be signed. Inputs and displayed results use at most three decimal places.
Worked examples
See the method in practice
Finding net force
A 5 kg object accelerating at 3 m/s² requires a net force of 15 N in the acceleration direction.
Finding acceleration
A net force of −20 N acting on a 4 kg mass produces an acceleration of −5 m/s² along the selected axis.
Questions
Frequently asked
Is this force the applied force?
Only when no other force contributes along the chosen axis. In general, use the vector sum of all external forces.
Why can force or acceleration be negative?
A negative sign indicates direction relative to the positive axis you selected; it does not mean the magnitude is physically negative.
Does the calculator include weight or friction automatically?
No. Resolve weight, friction, tension, normal force, and other forces first, then enter their net component along the axis.
Sources & review
Equations and examples are checked against the references below. Results are educational and should be independently verified for safety-critical work.
OpenStax University Physics — Newton’s Second LawWritten by the STEM Hub editorial team · Reviewed August 11, 2026 · Review methodology