Calculators
Momentum Calculator
Solve momentum, mass, or velocity with unit conversion.
Momentum Calculator tool
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About This Tool
Linear momentum describes an object's quantity of motion and, unlike kinetic energy, includes direction. In one dimension it is calculated as momentum equals mass multiplied by velocity, p = mv. This calculator solves the relationship in all three directions and converts common mass, velocity, and momentum units automatically. Positive and negative velocity values can represent opposite directions along a chosen axis, and all calculations run locally in your browser.
How To Use It
- Choose whether to solve for momentum, mass, or velocity.
- Enter the two known values and select their units. Mass must be positive; velocity and momentum may be signed to represent direction.
- Choose a result unit and read the calculated value and formula.
- For multi-dimensional motion, calculate vector components separately or use an appropriate vector method; this tool models one-dimensional signed motion.
Examples
Basic momentum
A 2 kg object moving at 3 m/s has p = 2 × 3 = 6 kg·m/s.
Opposite direction
If the same 2 kg object moves at -3 m/s relative to the chosen positive axis, its momentum is -6 kg·m/s.
Convert speed first
A 1 kg object moving at 36 km/h is moving at 10 m/s, so its momentum is 10 kg·m/s.
Find velocity
An object with momentum 12 kg·m/s and mass 4 kg has velocity 3 m/s because v = p/m.
Useful Notes
Momentum formula
Classical linear momentum is p = mv, where p is momentum, m is mass, and v is velocity. Rearranging gives m = p/v and v = p/m.
Momentum has direction
Momentum is a vector quantity. In a one-dimensional calculation, the sign can encode direction: positive and negative momentum point in opposite directions according to the coordinate axis you define.
Momentum units
The SI unit is kg·m/s, which is dimensionally equivalent to N·s. This calculator also supports g·m/s and lb·ft/s for convenient conversion.
Momentum versus kinetic energy
Momentum depends linearly on velocity and includes direction, while classical kinetic energy is ½mv² and is scalar. Two objects can therefore be compared differently depending on which quantity matters to the problem.
Model limitations
This tool calculates classical translational momentum for a single mass and one-dimensional velocity. It does not model collisions, impulse over time, relativistic momentum, rotating systems, or multiple vector components.
FAQ
Can momentum be negative?
Yes. A negative sign can represent motion in the direction opposite to the positive axis you chose. The mass itself remains positive.
What is the SI unit of momentum?
The SI unit is kilogram metre per second (kg·m/s). It is also equivalent in dimensions to a newton-second (N·s).
Is momentum the same as force?
No. Momentum describes motion, while net force is related to the rate of change of momentum over time.
Can an object at rest have momentum?
In classical mechanics, an object with zero velocity has zero linear momentum because p = mv.