Also might look at this thread:

viewtopic.php?f=7&t=11185 there is a link at the end to a newsletter that has a guide to building a canon shooting type of game.

Also, if you want a calculated path, sin and cos can be used to generate factors that can then be used to calculate a trajectory.

Just off the top of my head.. Determine the angle of launch. use sin and cos to create x, y factors, use those factors unchanged combined with your launch velocity you can move the object in a straight line. Since you want it to be a ballistic trajectory, the y factor can be modified by taking the force of gravity and again to 'tweak' the value of y, adjusting for gravity over time. I think.