Question about addForce()

I've been using unity for quite a while now. And I've noticed that the `addForce()` of a rigidbody applies a constant force.

Q1: Can I apply a short force impulse (like box2d's `ApplyImpulse`)?

Q2: Can I apply variable acceleration (like a car accelerating)?

In addForce you can specify the forcemode as a parameter. So for example:

rigidbody.AddForce (Vector3.up * 10, ForceMode.Impulse);

Some (breif) details of the different forcemodes can be found here:

http://unity3d.com/support/documentation/ScriptReference/ForceMode.html

You can use the same for acceleration.

Edit: Final note - make sure you are doing all of this in FixedUpdate()