Momentum
Momentum is the product of an object's mass and velocity, describing how hard it is to stop.
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Momentum is the product of an object's mass and velocity, describing how hard it is to stop.
- p equals m v
- It is a vector
- Measured in kilogram metres per second
🧠 Quick quiz
Three questions. Score 2 or more to complete the topic.
What is Momentum?
Within Physics, which covers forces, energy, waves, electricity, magnetism, light and space explained through motion and experiments, this topic explains Momentum. Physics topics explain how things move, push, heat up and carry energy, so each one here pairs a definition with a live model you can change.
Check that you can explain Momentum in your own words and give one example from everyday life. If you can do that, you have understood the core idea.
Understanding Momentum explains how the physical world behaves, from sport and transport to electricity and medicine.
Momentum in detail
Momentum is the product of mass and velocity: p = mv, measured in kg m/s. It is a vector, so it has the same direction as velocity. A heavy lorry and a fast cricket ball can both have large momentum.
Newton's second law can be written as force = rate of change of momentum, so a larger force or a longer time changes momentum more. Momentum explains why it is harder to stop a heavy or fast-moving object, and it is used in analysing collisions, rockets and sport impacts.
How the interactive helps you understand Momentum
Watch the force arrows in the interactive. Use any sliders or buttons it offers to change the values and see how the force arrows responds.
Before you change anything, predict the result. Then change one value at a time and check whether your prediction was right. This is a quick way to build a correct mental model of Momentum.
Real-life uses and examples
- Predict what a ball, car or circuit will do with Momentum before you do the calculation.
- Explain everyday devices, such as brakes, lifts or chargers, using Momentum.
- Use Momentum to make sense of a practical and its results.
Common mistakes to avoid
- Mixing up Momentum with a related quantity that has different units.
- Forgetting that some quantities, such as force or velocity, also have a direction.
- Learning the definition without testing it. Use the quiz and the interactive to check that you can apply the idea.
Frequently asked questions about Momentum
What is Momentum?
Momentum is the product of an object's mass and velocity, describing how hard it is to stop.
What are the most important points about Momentum?
The main points are: p equals m v; It is a vector; Measured in kilogram metres per second.
Why is Momentum useful?
Understanding Momentum explains how the physical world behaves, from sport and transport to electricity and medicine.
How can I practise Momentum?
Open the interactive at the top of this page and change the controls one at a time. Predict the result before each change, then take the three-question quiz. A score of two or more marks the topic as complete on this device.
Which topics are related to Momentum?
Related topics in Physics include Circular Motion, States of Matter and Changes, Latent Heat.