Momentum Calculator: p = mv

Find the momentum of a moving object, or its mass or speed.

Calculated from standard textbook formulas, with every step shown. The formulas are fixed, so the working does not need checking: what matters is the numbers you type in. Use these calculators only if you are competent to choose the inputs (loads, material strength, dimensions, supports) and check your units and assumptions. For learning and checking your own working: design and sign-off are for a qualified engineer. Drafting Central does not store the numbers you type.

How this calculator works

Choose which quantity you want to find.

Enter the other values in the units shown.

The calculator gives the answer with the formula, the substituted numbers, and the answer in other units.

Formulas used

  • p = m\,v
  • m = \frac{p}{v}
  • v = \frac{p}{m}

Worked example

With the default numbers in the calculator above:

  1. The formula, arranged to find the momentum: momentum = mass x velocity
  2. Put the values in (every value in its SI unit): momentum = 0.145 x 40
  3. The answer: momentum: 5.8 kg m/s
  4. The same answer in other units: 5800 g m/s; 41.9515 lb ft/s

Change the numbers in the calculator to see the full working, every step, for your own case.

Common questions

What is the formula for momentum?

Momentum equals mass times velocity. A 0.145 kg baseball at 40 m/s has 5.8 kg m/s.

What is conservation of momentum?

In a collision with no external forces, the total momentum before equals the total after.

What is the unit of momentum?

Kilogram metres per second, which is the same as newton seconds.

Related calculators

Got a question about this? Ask an engineering question and get a plain-language answer with references.

Further reading: Any school physics text (momentum).

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