# rotate and points on shape

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Hi everyone, Im new here :) Im currently working on a 2D physics engine, but am having some trouble. If I have an object and shoot it at a certain point, how would I calculate the speed and angle it would fall/rotate? Also, Ive seen some examples of physics engines, and nearly all of them have large verteces (sp?) at key points of the shape. For example, a square would have four verteces at the corners. What are these used for and how can I use them in game? Thanks for any help.

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What do you mean by 'large vertices'? I'm not sure I understand that part of the question, but for a good introduction to 2d rigid body dynamics, take a look at this (a little down the page, under 'physics articles').

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Thanks for the reply. Sorry, my post wasnt too clear. Basically, Ive noticed in some demos that a square would have four points at the corners, which the user can sometimes drag with. Im not sure if these points are also used in the alignment of the object with a slope. I basically just wanted to know how to make an object (such as the square) line up at the same angle as a slope if it was dropped onto the slope. From there, I could try and see whether the square would topple over and slide down the slope.
That link is useful and Ive gotten through the first part, but when it comes to the angular velocity stuff, it gets a bit confusing.

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