Free · Force calculators 💪

Net Force from Velocity Change & Mass

Connect constant mass, velocity change, elapsed time, average acceleration and average net force along one axis.

  • Formula & worked example
  • Private in your browser
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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

A 2 kg mass changing from 0 to 36 km/h in 5 seconds has average acceleration 2 m/s² and average net force 4 N.

a = (final velocity − initial velocity) / elapsed time; F = ma

Worked example

Enter these known values and leave the other values blank.

Constant mass
2 kg
Initial signed velocity
0 km/h
Final signed velocity
36 km/h
Positive elapsed time
5 sec
Average signed acceleration
2 m/s²
Average net force
4 N

Assumptions and limitations

  • Choose one positive axis and use signed velocity components along that axis. Mass and elapsed time must be positive.
  • For constant mass, velocity change divided by elapsed time gives average acceleration and therefore average net force. It does not determine every instantaneous force.
  • Use the resultant of all forces when working backward from force. A negative result points opposite the chosen positive axis.

Common questions

Does a negative force mean an error?

No. It indicates the force component points in the negative direction of your chosen axis.

Can I use changing mass?

This form assumes constant mass. Variable-mass systems require an appropriate momentum balance.

References

Bookify requires positive elapsed time for a physically meaningful velocity-change interval. Feet per second squared use exactly 0.3048 meters per second squared, replacing a rounded reciprocal factor. The pound-force uses the exact international pound and standard gravity instead of the rounded captured factor. The poundal uses exactly one international pound-foot per second squared.

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