Momentum
moh-MEN-tum
/moʊˈmɛntəm/
The quantity of motion of a moving body, measured as a product of its mass and velocity.
Momentum is a vector quantity (like velocity) and is conserved in a closed system. It's a measure of how hard it is to stop an object.
The story behind the word. "Momentum" comes from the Latin "momentum," meaning "movement, moving power, a brief space of time." It's related to "movere" (to move) and "moment" (a small division of time, a turning point). The idea of a "moving power" or "impulse" evolved into its precise physical definition.
Word relationships
- impetus: "Impetus" refers to the force or energy that makes something move or happen, often implying a driving force, while momentum is the quantity of motion itself.
- drive: "Drive" can mean energy or determination, often metaphorical, less precise than "momentum."
- inertia (in a metaphorical sense): While related, inertia is resistance to change, momentum is the quantity of motion. Metaphorically, inertia can oppose momentum.
- stagnation: A state of no progress or movement, opposite to gaining momentum.
Commonly confused with
- Kinetic Energy: Momentum (mv) is a vector and conserved in collisions; Kinetic Energy (1/2 mv²) is a scalar and often converted to other forms in collisions.
Word family
- moment (noun): A brief period of time; importance (related to "movement" in older sense).
Collocations
- linear momentum
- angular momentum
- conservation of momentum
- gain momentum
- lose momentum
Idioms & expressions
- gather momentum
- lose momentum
- keep the momentum going
Example sentences
- "The bowling ball, despite its moderate velocity, had significant momentum due to its large mass." Describing a collision.
- "The team gained momentum in the second half, scoring three quick goals." From a sports commentary. (ESPN Sports Commentary)
Memory hook
A MOMENTUM-ous event is one that keeps things MOVING forward. Moving Moment
When not to use
Do not confuse "momentum" with "kinetic energy." Both relate to motion, but momentum is mass x velocity, while kinetic energy is 0.5 x mass x velocity².
Fun facts
- The principle of conservation of momentum is fundamental to understanding collisions and rocket propulsion.
- In physics, momentum is often represented by the letter 'p'.
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