Momentum Calculator
Momentum captures both how much mass is moving and how fast — a slow-moving truck and a fast-moving car can carry comparable momentum, which is exactly why momentum, not just speed, determines collision severity.
Inputs
Result
30,000 kg·m/s
How it works
p = m × v
How the momentum calculator works
p = m × v, giving momentum in kg·m/s.
Worked example: 1,200 kg car at 25 m/s
- p = 1,200 × 25 = 30,000 kg·m/s.
- A much lighter 300 kg motorcycle would need to travel at 100 m/s (360 km/h) to match that same momentum — an extreme and unrealistic speed, illustrating how much mass alone contributes.
Common mistakes to avoid
Treating momentum as interchangeable with kinetic energy
Momentum scales linearly with velocity (double the speed, double the momentum), while kinetic energy scales with velocity squared (double the speed, quadruple the energy) — they behave very differently as speed increases.
Forgetting momentum is a vector
Direction matters for momentum — two equal masses moving toward each other at the same speed have momenta that cancel (sum to zero), not add, when treated as a system.
Frequently asked questions
Why does momentum matter in collisions specifically?
Total momentum of a closed system is conserved before and after a collision — this conservation law is what lets you calculate outcomes like how fast two vehicles move after impact, without needing to know the details of the collision force itself.
How is momentum different from force?
Momentum is mass times velocity (a property of motion); force is what changes momentum over time (F = change in momentum ÷ time) — force causes a change in momentum, it isn't momentum itself.
Does a heavier, slower object always have more momentum than a lighter, faster one?
Not necessarily — it depends on the specific numbers. A 2,000 kg truck at 5 m/s (10,000 kg·m/s) has less momentum than a 1,000 kg car at 15 m/s (15,000 kg·m/s), despite being far heavier.
What's the unit of momentum in words?
Kilogram-metres per second (kg·m/s) — there's no separate named unit for momentum the way there is for force (newtons) or energy (joules).
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