Force Law vs Speed Definitions
Introductory physics mixes two clean algebraic stories: net force related to mass and acceleration, and average or constant speed related to distance and time. Keep the stories separate so the right inputs feed the right unknown.
F Is Net Force
In F = ma, F is the net force along the direction of acceleration. If friction or another force is present, include it in the net total—or justify why it cancels—before solving.
Consistent SI Units
Use kilograms, meters, seconds, and newtons together. Mixing grams with meters per second squared without converting will invent the wrong force.
Which Branch to Use
| Question | Branch | Core formula |
|---|---|---|
| How hard is the net push? | Force | F = m × a |
| What mass fits this force and a? | Force | m = F ÷ a |
| How fast on average? | Speed | v = d ÷ t |
| How far at constant speed? | Speed | d = v × t |
Solve a force or speed unknown
Choose the unknown and enter the two knowns:
Open Physics Force Calculator