The Physics are controlled by the radius and the position of the force. Just animate it by sending a few keyframes. There are a few shatter tutorials on the web. It's pretty easy to figure out.
Like I said previously "Problem is when I apply the shatter effect to my Shape I created, it assumes I want the explosion to occur as soon as the video starts to play." This is not what I want. I need a key frame to initiate the explosion about 25 frames into the clip. The physics controls the location on the screen and the direction of the explosion, but to my knowledge it does not control the timing of the explosion. I have viewed Lynda tutorials repeatedly.
The tutorials make it look like it is possible to start an explosion later in the timeline but there is no explanation of how he did it. It looks like the explosion should occur when the "Shape" occurs in the time line, but After Effects is not working that way for me.
Quick and dirty workaround.
Split the layer into two at the point you want it to start.
You did not follow my instructions or experiment with the force parameters.
In the wireframe mode go to frame 25 and enable keyframes for force 1 position and radius. Now move back one frame to frame 24 and adjust the size and position of force 1 so it is behind the layer and small enough to not touch the later. If Force 1 and 2 do not touch the layer it can't shatter.
Shatter is based on real world physics and as soon as that clicks in your head you will be able to do amazing things.
They key frames made it work, now I can begin experimenting. Thanks so much