I intend to talk about forces and force diagrams, but there is a more fundamental question to address first. What is a force? Most texts define it as a push or a pull. That really isn't a bad definition. Maybe a better (or maybe worse) definition would be "forces are things that change the motion of an object" (change being the key word). If I had to choose one definition of force, it would be something like this:
**Force:** *A force is an interaction between two objects. There are 4 known forces:*
- Gravitational force: An attractive long range force between objects with mass
- Electromagnetic force: An attractive or repulsive long range force between two objects with charge
- Strong Nuclear force: An attractive short range force between particles like protons and neutrons
- Weak Nuclear force: A short range force responsible for beta decay. *Yes, I know that is a confusing force - for introductory physics, you won't use this force*
All forces are some form of the above forces.
**Important properties of forces**
- Forces are an interaction between TWO objects. It is not possible to have a force on an object and not have another object involved.
- Forces are vectors. They have magnitude and direction
- The unit for force is the Newton. If you do a whole bunch of cool stuff, they will name something after you also.
- Forces are NOT properties of an object like mass or speed or color. They are properties of an interaction between two objects. Yes, I already said that, but it is important.
There are some more things about force you will need to know. For now, this should be enough.
very basics of forces. Its very important.