Physics · BEGINNER LESSON
Momentum
Momentum is a physical quantity equal to an object’s mass multiplied by its velocity. In a closed system, the total momentum stays constant, even when objects collide or push on each other.
What momentum is
Momentum is a way to measure motion. For a single object, it depends on two things: mass, which is how much matter the object has, and velocity, which is speed in a chosen direction. Because direction matters, two objects with the same speed can have different momentum if they move differently. NASA describes momentum as mass multiplied by velocity, and says the total momentum of a closed physical system is conserved. [1]
[2] science.nasa.gov · universe · glossaryUniverse glossary - NASA Science
How momentum changes and why conservation matters
A collision changes the speeds and directions of objects, but the total momentum before and after the interaction can remain the same if the system is closed. That is why momentum is useful for analyzing impacts and other interactions. In the nucleon, a bound group of quarks and gluons, researchers describe momentum as flowing through space: there are contributions from the motion of particles and from forces between them. This is a more advanced field picture of conservation, but it still follows the same idea that momentum is not created or destroyed inside the closed system. [1,2]
[2] science.nasa.gov · universe · glossaryUniverse glossary - NASA Science [3] Momentum Flow Mechanisms and Color-Lorentz Forces on ...
Related ideas and limits
Angular momentum is a related quantity for rotating systems. The sources also describe momentum flow, which is a continuous picture of how momentum density moves through a system. These are not separate everyday meanings of momentum; they are more detailed ways to study it. A limitation is that momentum conservation is stated for closed systems, so outside influences can change the total momentum of the object group you are studying. [1,2]
[2] science.nasa.gov · universe · glossaryUniverse glossary - NASA Science [3] Momentum Flow Mechanisms and Color-Lorentz Forces on ...
A note on a different use of the word
One source uses the phrase temporal momentum for a psychology effect in time reproduction tasks, where arithmetic operations bias reported duration. That is a different concept from physical momentum in mechanics. [0]
[1] Temporal momentum: an online replication and beyond - PMC - NIH
SEE THE IDEA
How physical momentum is used
Has mass and moves with a velocity.
Mass multiplied by velocity; a measure of motion.
No outside influence, so total momentum stays constant.
Objects exchange momentum, but the total can remain unchanged.
Object has momentum; interactions redistribute it; in a closed system the total is conserved.
A simple conservation picture: momentum can move between objects, but the total in a closed system stays the same.
TRY IT YOURSELF
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PUT IT TOGETHER
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Sources and further reading
This general lesson was generated from public source material. It explains a concept; it does not interpret a private paper or provide medical advice.