Case 1
- Mass
- 10kg
- Speed
- 5m/s
50.000kg·m/s
Open with these valuesMomentum Calculator
50.000kg·m/s
Result: 50.000 kg·m/sMass times speed, and nothing else. A 10 kg object at 5 m/s carries 50 kg·m/s; double the speed and the momentum doubles too — unlike kinetic energy, which quadruples. The result is the magnitude, so set the sign yourself if you are tracking direction.
The numbers at a glance
Held fixed: Mass 10.000 kg.
| Speed (m/s) | Result (kg·m/s) |
|---|---|
| 0.000 | 0.000 |
| 2.000 | 20.000 |
| 4.000 | 40.000 |
| 5.000Your value | 50.000 |
| 6.000 | 60.000 |
| 8.000 | 80.000 |
| 10.000 | 100.000 |
Worked examples
Case 2
- Mass
- 0.145kg
- Speed
- 40m/s
5.800kg·m/s
Open with these valuesCase 3
- Mass
- 1000kg
- Speed
- 20m/s
20,000.000kg·m/s
Open with these valuesHow it's calculated
p = m × v
- StepEnter the mass in kilograms.
- StepEnter the speed in metres per second — divide km/h by 3.6.
- ResultRead the momentum in kilogram-metres per second.
What this number means
Momentum grows in step with the speed
Doubling the speed doubles the momentum and nothing more: 1000 kg at 20 m/s carries 20000 kg·m/s, and at 40 m/s exactly 40000. Kinetic energy squares the speed and would quadruple instead.
A brick and a baseball land almost level
Mass and speed count equally here, so very unlike objects meet: a 2 kg brick at 3 m/s gives 6 kg·m/s and a 0.145 kg baseball at 40 m/s gives 5.8. Kinetic energy, with its squared speed, would rank the two far apart.
The sign is yours to set
Momentum is a vector, but the speed box rejects negative values, so what comes out is the magnitude. In a head-on collision the two objects need opposite signs before the totals can be added.
Conservation is what makes it useful
In a closed system with no outside forces the total stays constant, so whatever one object loses in a collision the other gains. Kinetic energy has no such guarantee — it can leave as heat, sound or deformation.
Commonly misread
Twice the speed means four times the momentum.
That rule belongs to kinetic energy, which squares the speed. Momentum is linear, so twice as fast is exactly twice as much: 20000 kg·m/s becomes 40000.
Momentum is always positive.
It is a vector, and its sign follows the direction of travel along whichever axis you pick. This calculator reports the magnitude, so you attach the sign yourself.
In a collision both objects lose momentum.
In a closed system the total cannot change: what one object loses the other gains, so the sum before and after the collision is identical.
Reference table
| Mass, speed | Example | Momentum (kg·m/s) |
|---|---|---|
| 1, 1 | One kilogram, walking pace | 1 |
| 2, 3 | A brick, thrown | 6 |
| 0.145, 40 | Pitched baseball | 5.8 |
| 10, 5 | Bowling ball down the lane | 50 |
| 1000, 20 | Small car at 72 km/h | 20000 |
Questions
How do I calculate momentum?
Multiply the mass by the velocity: p = m × v. Use kilograms for mass and metres per second for velocity to get the answer in kg·m/s. For example, a 10 kg object at 5 m/s has 10 × 5 = 50 kg·m/s.
What is momentum?
Momentum is a measure of how much motion an object has — its mass times its velocity. The heavier or faster an object is, the more momentum it carries, and the harder it is to stop or change its direction. It is measured in kilogram-metres per second (kg·m/s).
What is the difference between momentum and kinetic energy?
Momentum is mass times velocity (p = mv) and grows in proportion to speed, while kinetic energy uses velocity squared (½mv²) and grows much faster. Momentum is a vector with direction and is conserved in collisions; kinetic energy is a scalar measured in joules and can convert into heat, sound, or deformation.
Is momentum conserved?
Yes. In a closed system with no outside forces, the total momentum stays constant. When two objects collide, the momentum lost by one is gained by the other, so the combined momentum before and after the collision is the same.
What units should I use for momentum?
Use SI units: kilograms for mass and metres per second for velocity, which gives momentum in kilogram-metres per second (kg·m/s). If your speed is in km/h, divide by 3.6 to convert to m/s first. Momentum has the same units as impulse, which is force multiplied by time.
Can momentum be negative?
Momentum is a vector, so its sign depends on direction. An object moving to the right has positive momentum and one moving to the left has negative momentum along that axis. This calculator works with speed in one direction, so it reports the magnitude — the size of the momentum regardless of direction.
Sources and last check
Information, not professional advice.