momentum collision formulas and interpretation
In an isolated collision, total linear momentum is conserved.
The legacy interface supports collision cases while retaining signed velocities for direction.
How to use the momentum collision calculator
- Choose a model: Select the relationship matching the problem.
- Choose the unknown: Select the quantity to calculate.
- Enter values: Enter all known values with matching units and signs.
- Calculate: Review the result, formula, units, and direction.
Formula and variables
For a perfectly inelastic collision, combined final velocity follows momentum conservation.
m₁v₁ + m₂v₂ = (m₁+m₂)vf- m₁,m₂ — Masses
- Colliding object masses (kg)
- v₁,v₂ — Initial velocities
- Signed velocities before collision (m/s)
- vf — Final velocity
- Combined velocity after collision (m/s)
Inelastic collision example
A 2 kg object at 6 m/s sticks to a 4 kg stationary object.
- First momentum
- 12 kg·m/s
- Combined mass
- 6 kg
- vf = 12 / 6
- vf = 2 m/s
Result: Final velocity is 2 m/s.
Both objects move together at 2 m/s.
Understanding your results
Interpreting the result
Velocity signs determine the net momentum direction.
Assumptions
- The selected equation represents the physical system.
- Inputs use a consistent reference direction.
- Values are converted through coherent SI units.
Limitations
- Vector components must be resolved along a common axis.
- External forces or energy losses are not added automatically.
- Results depend on the accuracy of entered measurements.
Common mistakes
- Mixing incompatible units.
- Dropping negative signs that represent direction.
- Using weight where mass is required.
- Entering a zero divisor.
Practical use cases
Physics problems
Check classroom, laboratory, and mechanics calculations.
Practical estimates
Estimate motion, forces, and energy for real systems.
Frequently asked questions
Can a result be negative?
Yes. For directional quantities, the sign indicates direction relative to the chosen positive axis.
Should I use SI units?
The interface can convert supported units, while the formulas are evaluated through coherent SI units.
Sources and review
- SI Brochure, 9th edition — BIPM. Accessed 2026-07-11.
- Special Publication 811 — NIST. Accessed 2026-07-11.
Reviewed 2026-07-11.