Collision Handling for moving rectangles

in my Silverlight 3 application, I display a tree. A self made user control is used for the treenodes, the LineArrow object for the connections. After initial displaying the tree, I want the nodes to move by the following "physical properties"

there is a gravitational force, that pulls the node down
there is a force vector to its parent
it's children draws it to their middle

Naturally, my User Controls will overlap soon. But I do not want them to overlap. In physics terms, I want them to be solid objects and enforce the physical rule that no 2 objects can inhabit the same space.

Any suggestions how to tackle this problem? I do not want to use a physics engine like farseer for this, because the described part is the only physics to be used within my project.

Thanks in advance,
Frank

Solution

You can model them as 'nearly solid' objects simply by adding a very large force between them whenever they overlap. Calculate the center to center vector, normalize it, maybe multiply by the overlap and then apply that as a force to each object.

Even if you don't use the full Farseer library you may still find some useful classes in it like Vector2.