Library / Foundations: Physics / FPH-05
Foundations: Physics
Momentum
Mass times velocity.
- Ref
- FPH-05
- Rev
- v1
- Field
- Foundations: Physics
- Result
- p [kg·m/s]
Momentum has direction. Total momentum is conserved if the net external impulse is zero.
Momentum measures how hard it is to stop a moving object: heavier and faster objects have more.
Calculator
kg·m/s
kg
m/s
- Kinetic energy375 kJ
- p²/2m (same energy)375 kJ
What drives the result
Each variable is moved across its typical range while the others stay at the values above. The longest bar is the key driver.
Momentum (kg·m/s) current value 30,000 kg·m/s
vVelocityKey driver
1,2001,200,000
mMass
0.25250,000
- In a collision the total momentum before equals the total after.
- A small fast bullet can have the same momentum as a slow heavy object.
Chart data as tables
Ranked variables
| Variable | Typical range | Lowest result | Highest result | Swing (kg·m/s) | Local step | Change in result |
|---|---|---|---|---|---|---|
| v Velocity | 1 to 1,000 m/s | 1,200 | 1,200,000 | 1,199,000 | +10% | +10 % |
| m Mass | 0.01 to 10,000 kg | 0.25 | 250,000 | 250,000 | +10% | +10 % |
Sweep of Velocity
| Velocity (m/s) | Momentum (kg·m/s) |
|---|---|
| 1 | 1,200 |
| 2.371 | 2,846 |
| 5.623 | 6,748 |
| 13.34 | 16,000 |
| 31.62 | 37,950 |
| 74.99 | 89,990 |
| 177.8 | 213,400 |
| 421.7 | 506,000 |
| 1,000 | 1,200,000 |
Sweep one variable
Momentum (kg·m/s)Hover, touch, or use the arrow keys on the chart
Variables and how each one contributes
p
Momentum
What the equation gives you. Everything else feeds it.
m
Mass
Mass of the object. Directly proportional.
v
Velocity
Velocity of the object. Directly proportional.
Worked example with the values above
- Mass 1,200 kg, velocity 25 m/s.
- Multiply them.
- p = 30,000 kg·m/s.
Assumptions and limits
- Speeds well below the speed of light.
- Direction chosen as positive.
Common mistakes
- Forgetting direction when adding momenta.
- Using weight instead of mass.
Statistics and uncertainty
Relative errors in mass and speed combine in quadrature; speed is often the weaker measurement.
Where it is used
- Recoil and collision calculations.
- Projectile momentum.
Maths you need
- Mass and velocity: basic quantities
- Vectors: direction matters