# Force and Mass

## Summary

- Newton's second law of motion (also known as the force law) states that…
- acceleration is directly proportional to net force when mass is constant, and…
- acceleration is inversely proportional to mass when net force is constant, and consequently…
- net force is directly proportional to mass when acceleration is constant.

- Newton's second law of motion is more compactly written as the equation…
∑

**F**=*m***a** - Mass
- Mass is a measure of resistance to acceleration. More generally, mass is a measure of resistance to all sorts of change.
- Mass is a scalar quantity associated with matter.
- When a system is composed of several objects it is the total mass that matters.
- The SI unit of mass is the kilogram [kg].
- The kilogram is one of the seven base units of the International System of Units

- Force
- A force is an interaction that causes acceleration. More generally, a force is an interaction that causes a change.
- A force is a vector quantity associated with an interaction.
- When several forces act on a system it is the net, external force that matters.
- The SI unit of force is the newton, named after the English physicist and mathematician Isaac Newton (1642–1727).
[N = kg m/s

^{2}]

- Supplementary Materials
- Summary as a concept map
- Original statement in Latin from Newton's Principia with English translation