In Physics, a Force Is Anything That Changes Motion
Force is strength or power. Physics defines it exactly: whatever changes an object's motion, measured in newtons.
Force is strength, power or compulsion, and in physics an interaction that changes an object's motion. Newton's definition is exact: force equals mass times acceleration, so a force is anything that makes something speed up, slow down or change direction. A book resting on a table is under force from gravity and an equal force from the table, which is why it does not move. The unit is the newton, defined as the force that accelerates one kilogram by one metre per second squared.
- Physical strength. *Excessive force.*
- A physical interaction. *Gravitational force.*
- A body of people. *The police force.*
- To compel. *Forced to resign.*
- Newton — the unit. *Ten newtons.*
Word forms
| Form | Word | Example |
|---|---|---|
| Noun | force | Great force. |
| Plural | forces | Armed forces. |
| Verb | force | Force it open. |
| Adjective | forceful | A forceful argument. |
| Latin | fortis | Strong. |
- The door was forced open.Physical.
- Gravity is a fundamental force.Physics.
- The law comes into force in April.Legal.
The four fundamental forces
- Gravity — weakest, but acts over infinite range
- Electromagnetism — binds atoms into molecules
- Strong nuclear force — holds atomic nuclei together
- Weak nuclear force — governs certain radioactive decays
- Everything else — friction, tension, pressure — reduces to these
Old French *force*, from Vulgar Latin *fortia*, from Latin *fortis*, strong. The same root gives *fort*, *effort* and *comfort*.
What is a newton?
The force needed to accelerate one kilogram of mass by one metre per second squared. Roughly the weight of an apple.
Are force and comfort related?
Yes. Comfort comes from Latin com plus fortis, to strengthen greatly.