Look at videos of robots playing pool. Perfectly straight strokes, but the shots are also programmed and everything is lined up correctly.
Now what happens if they line up the robot incorrectly (say off by 2")? The shot will be missed. But why? The stroke was perfectly straight.
Now what happens if they line up the robot incorrectly (say off by 2")? The shot will be missed. But why? The stroke was perfectly straight.