Sorry if this sounds like a dumb question, but I can't understand why something would rotate. Ex. with a two particles connected by a rod, if a force is applied anywhere other than its center of mass, the same force would cause both translation and rotation. Also, how come if the same force is acted onto the center of mass of the object described above, it would move at the same rate linearly as if the force was applied anywhere else, so it seems the rotational motion doesn't require any work, what's the explanation for this? Thanks.