1. The problem statement, all variables and given/known data Referring to the attached diagram, the object ABCD is kept in an isolated system where it is under no external influence of any kind. A· An instantaneous force F acts along the edge BC of the block ABCD, where M is its mass, with its center of mass located at O. B· X-Y is the coordinate system that has been used to resolve the aforementioned force C· The component of force towards O (F cosθ) is further resolved using another coordinate system X'-Y'. Here are the questions: 1. Is choosing these kinds of coordinate systems legit in mechanics (meaning, one would intuitively take AB and BC as the X and the Y coordinates respectively. Would it be wrong if someone doesn't)? If yes, then: 2. Will ABCD have an instantaneous acceleration in the X' direction which is equal to (F cosθ(cosα))/M, when F is applied? 3. Will ABCD have an instantaneous acceleration in the Y' direction which is equal to (F cosθ(sinα))/M, when F is applied? 4. What will the F sinθ do (i.e will it have any effect on the motion of ABCD)? 5. Which component of the force F will cause rotation in ABCD and about which point? 6. If the edges BC and AD are reduced to 0, then will F cause pure rotational motion and no translation motion? 2. Relevant equations No such equations 3. The attempt at a solution I intentionally framed this question in my head so that the concept of choosing coordinates becomes clearer. So, as such I have not reached a solution as yet.