Momentum Calculator
Momentum, collisions, impulse, and rocket Δv—with conversions and checks.
How to Calculate Momentum
Momentum describes how much motion mass carries. In collisions, total momentum is conserved when external forces are negligible. Elastic collisions also conserve kinetic energy; inelastic collisions do not—energy becomes heat, sound, and deformation. Impulse links average force and contact time to the change in momentum. Use the Momentum Calculator to get a clear result you can act on right away. This calculator is designed to be practical, fast, and easy to use on any device. If you are comparing options, run a few scenarios to see how small changes affect the outcome.
Momentum
30,000 kg·m/s
p = m v = 1,500 kg × 20 m/s
• 30,000 kg·m/s (= N·s)
• 30 kN·s
• 6,744.27 lbf·s
Kinetic energy KE = ½mv² ≈ 300,000 J (300 kJ)
If stopped in 4 s (constant braking model): |F̄| ≈ 7,500 N (1,686.07 lbf)
| Example | |p| (kg·m/s) |
|---|---|
| Baseball pitch (~90 mph) | 5.9 |
| Running person (illustrative) | 560 |
| Bicycle (illustrative) | 1,800 |
| Small car (~30 mph) | 21,000 |
| SUV (~60 mph) | 80,000 |
| Semi truck (~60 mph) | 360,000 |
Your momentum: 30,000 kg·m/s
💡 Tips
- •Use consistent units; this calculator converts inputs to kilograms and meters per second for the core formulas.
- •One-dimensional models assume motion along a line; signs indicate direction.
- •The rocket equation uses initial and final mass while exhaust speed stays fixed—an idealization.
- •Real impacts are rarely perfectly elastic; results are best thought of as models.
🎉 Fun Facts
- •In an isolated system, total momentum is conserved—one of the core laws of mechanics.
- •Impulse equals change in momentum: J = Δp = F̄Δt for constant average force.
- •Inelastic collisions conserve momentum but generally lose kinetic energy to heat and deformation.
- •Elastic collisions conserve both momentum and kinetic energy (idealization).
- •Rockets accelerate by expelling mass backward; momentum conservation pushes the vehicle forward.
- •Airbags increase stopping time, lowering peak force for the same momentum change.
- •Newton's cradle is a familiar demo of nearly elastic momentum transfer along a line.
- •Momentum is a vector: direction matters; opposite momenta can cancel.
- •The rocket equation relates speed gain to exhaust speed and the natural log of the mass ratio.
- •Real collisions are rarely perfectly elastic; pool balls are close on short time scales.