The equations
- v = v₀ + a·t
- Δs = v₀·t + ½·a·t²
- v² = v₀² + 2·a·Δs (Torricelli)
v₀ is the initial speed, v the final speed, a the acceleration, t the time and Δs the distance. They work only when the acceleration is constant.
Examples
A car starts from rest (v₀ = 0) and accelerates at 2 m/s² for 5 s: it reaches 10 m/s (36 km/h) and travels 25 m.
A car at 20 m/s brakes and stops in 40 m: its acceleration is −5 m/s² and it takes 4 s to stop.
For a trip at an average speed, use the average speed calculator.
Frequently asked questions
What does a negative acceleration mean?
The object is slowing down (when it moves in the positive direction).
How do I convert km/h to m/s?
Divide by 3.6. 72 km/h = 20 m/s.
And for a falling object?
Use a = 9.81 m/s² (gravity) and v₀ = 0 if it is dropped. Air resistance is ignored.
See also
Results are estimates for information only and are not financial, legal or medical advice. Rates, taxes and fees vary — confirm with a professional or your lender.