Momentum Calculator
Calculate the linear momentum of any object using p = mv. Enter mass in kilograms and velocity in metres per second to find momentum in kg m/s. Useful for physics students and engineers studying collisions and motion.
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How to use this tool
- Enter mass and velocity in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your momentum and the full breakdown beneath it.
Formula
p = m * v
How it works
Momentum p is the product of an object's mass m (kg) and its velocity v (m/s). It is a vector quantity sharing the direction of velocity.
Worked examples
Baseball pitch
Car on highway
Common mistakes to avoid
- Entering mass in grams instead of kilograms — 1 g = 0.001 kg, so forgetting to convert overstates momentum by a factor of 1000.
- Using speed (magnitude only) when the object is moving in a specific direction — momentum is a vector quantity p = mv, so direction matters in collision problems.
- Confusing momentum with kinetic energy; KE = (1/2)mv^2, which has different units (joules) and a velocity-squared dependence.
Key terms
Frequently asked questions
- What are the SI units of momentum?
- The SI unit is kilogram-metres per second (kg m/s), also written as newton-seconds (N s) since 1 N s = 1 kg m/s.
- How is momentum used in collision analysis?
- In any isolated collision, total momentum is conserved: p_before = p_after. For two objects, m1*v1 + m2*v2 = m1*v1' + m2*v2'. This lets you find unknown post-collision velocities.
- Can momentum be negative?
- Yes. Momentum is a vector, so a negative value simply means motion in the opposite direction to the positive reference. In 1D problems this is common when two objects move toward each other.