Rigidbody.AddForce is in what units?

What units is Rigidbody.AddForce in?

For example, are dir.x in m/s^2:

myRigidBody.AddForce (dir.x, dir.y, 0, ForceMode.Acceleration);

Yes, the unit of distance in Unity is meters per default. So acceleration will be in meters per second squared. Force in newtons. Velocity in meters per second.

Notice that the only constant in the system which dictates this is the default gravity - which you can change in the player settings. By doing so, you can make the units whatever you want - they are all just relative.

In the Unity editor: Edit > Project Settings > Physics > Gravity

I believe I'd heard that 50 units of force translates to 1 unit of distance per second per second.