I have an argument with classmates about the trajectory that the block will have (circle, ellipse, something else...). The configuration is similar to this image. http://minireference.com/_media/physics/momentum-bullet-speed-block.jpg?w=400 Initially, the block will move horizontally, after which it will move up as well, since the strings have constant length. But will the path be a circle, an ellipse, or another shape? I believe it will be a circle because the ropes will always be parallel and the middle axis of the parallelogram formed by these two ropes will also have constant length. So the distance of the middle point on top of the block to the ceiling is constant, which means it's a circle. They believe it should be an ellipse, because the strings might not be always taut. Which is true?