Linear Momentum
Momentum is mass times velocity: p = mv.
About this topic
Momentum is the product of mass and velocity, p = mv, a vector measured in kg·m/s. A heavy slow truck and a light fast bullet can have the same momentum. Newton's second law can be written as force = rate of change of momentum.
Momentum describes how hard something is to stop. It is the basis of collisions, explosions and rocket motion. The direction matters: a ball with 2 kg m/s moving right has momentum +2, while the same ball moving left has -2, so bouncing it back changes its momentum by 4.
Example: a 1500 kg car at 20 m/s has momentum 30,000 kg m/s, while a 0.01 kg bullet at 600 m/s has just 6 kg m/s, yet the bullet can be stopped by a thin barrier because the momentum is small. A tennis ball hitting a wall at 30 m/s and rebounding at 25 m/s changes its momentum by m x 55. Sports, car safety and astronomy all use momentum.
Tip: do not confuse momentum with kinetic energy; momentum depends on v and is a vector, while kinetic energy depends on v squared and is a scalar. Always assign positive and negative signs for directions.
Key ideas
- A vector quantity
- Heavy fast objects have large momentum
- Unit: kg·m/s
Quick check
Use cases: where Linear Momentum helps
- Homework: review the key idea behind Linear Momentum before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Linear Momentum without notes.
- Visual learning: play with the interactive lab to see how Linear Momentum changes when you adjust its inputs.
- Teaching a friend: explain Linear Momentum in your own words, then compare your version with the key ideas.
The same laws describe car crashes, sports, satellites and everyday machines.
Frequently asked questions
What is Linear Momentum?
Momentum is mass times velocity: p = mv.
What will I learn in Linear Momentum?
A vector quantity. Heavy fast objects have large momentum. Unit: kg·m/s.
Is Linear Momentum part of Physics?
Yes. It is one of 150 Physics topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Linear Momentum lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Linear Momentum?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.