Perfectly Inelastic Collision Calculator
Finds the common velocity after an ideal perfectly inelastic collision. On this Perfectly Inelastic Collision page, changing an entry updates the result and visible checking path.
Enter the observed quantities
Shared final velocity
Start with the energy or momentum picture
Finds the common velocity after an ideal perfectly inelastic collision. In energy-balance exercises, this relationship is meaningful only when the reference frame, direction convention, and units remain consistent.
The named fields are first mass, first velocity, second mass, second velocity. Each belongs in a defined position within v_f = (m₁v₁+m₂v₂)/(m₁+m₂); writing values beside the symbols helps catch a transposition.
On this Perfectly Inelastic Collision page, the sign of shared final velocity follows the stated axis, work, or rotation convention. Keep that convention unchanged from the inputs through the reported answer.
Following v_f = (m₁v₁+m₂v₂)/(m₁+m₂)
The worked case uses First mass = 2 kg, First velocity = 5 m/s, Second mass = 3 kg, Second velocity = 0 m/s. These values provide a reproducible example, and no unannounced unit conversion is applied to them.
Arrange v_f = (m₁v₁+m₂v₂)/(m₁+m₂) symbolically before substitution. That order makes an inverted ratio, omitted exponent, or misplaced number easier to identify.
Check direction, magnitude, and units
Start the dimensional check with v_f = (m₁v₁+m₂v₂)/(m₁+m₂). After cancellation, the surviving dimension must agree with m/s; a mismatch means the setup needs correction.
Then change one input by a controlled amount and predict how shared final velocity should respond before recalculating. Direction and sensitivity provide separate checks on the arithmetic.
Reading shared final velocity in context
The calculator reports shared final velocity in m/s. If that number enters a later formula, preserve guard digits until the final operation.
Compare shared final velocity with the scale of the perfectly inelastic collision scenario. A metric-prefix mistake or inconsistent time unit can produce tidy arithmetic that is physically implausible.
For reproducibility, record first mass, first velocity, second mass, second velocity, their units, the reference direction, and v_f = (m₁v₁+m₂v₂)/(m₁+m₂) rather than saving only the final numeral.
Where this model stops
The Perfectly Inelastic Collision model uses the stated one-dimensional quantities. Conservation requires negligible external impulse during the event, while rotation, deformation, sound, heat, or off-axis motion can change shared final velocity.
The precision of shared final velocity is limited by the least certain measurement. Extra displayed digits support verification, but safety-critical work requires validated data and a suitable engineering procedure.
A sensible next calculation
A useful follow-up is velocity from momentum calculator.
Choose the next calculator by the quantity still unknown; similar entries can belong to different energy models. Here, that choice follows from the perfectly inelastic collision result.
Questions about this calculation
What does the shared final velocity represent?
It is shared final velocity under v_f = (m₁v₁+m₂v₂)/(m₁+m₂) and the field definitions printed on this page.
How can the Perfectly Inelastic Collision answer be checked?
Rearrange v_f = (m₁v₁+m₂v₂)/(m₁+m₂) to recover one entered quantity, then confirm that the remaining unit is m/s.
Do these inputs need consistent units?
Yes. Match every value to the unit beside its field before applying v_f = (m₁v₁+m₂v₂)/(m₁+m₂).