How to allow Rigid Body Physics take over after follow path constraint? I'm trying to get a car to crash into a wall after a couple curves. I've followed Jonathan Lampel's tutorial on http://www.blender.org/support/tutorials/ which worked well using keyframes for animation. But is there a way to use the "Follow Path" Constraint and get the same effect? Or do I need to work in keyframes instead? 

I move to frame 70 (when object reaches end of path), keyframed the animation check box, moved to frame 71, unchecked the animation and keyframed the checkbox again (like done in the tutorial). When I run the animation the object goes down the path like I want, but as soon as hits frame 71, the object disappears and reappears really far away and just falls forever.

Anyone able to help me out? Don't want to make the whole thing with keyframes but can do that if no better way.
At the frame before you want to switch from the "follow path" to rigid body, keyframe the "Follow Path" Constraint influence to "1" by hovering over the influence slider and pressing "i". Then go ahead one frame and set the influence to "0" and keyframe the influence again.

Then to do the same thing on the same frames to your rigid body. (I believe the dynamic checkbox controls the rigid body the same way the influence slider would for the "follow Path", but I'm not 100% sure.)