"Why would a dog slam her head off the floor? My thirteen year old lab has recently slamming her head off the floor."<br/><br/>This is the question I found in Yahoo Answers.<br/><br/>Why not use 'onto' here instead of 'off'?<br/><br/>As far as I know, 'off' is one of those 'source' prepositons: it shows an initial position when there is a change of location.<br/><br/>For example,<br/><br/>ex1) He jumped off the bridge.<br/><br/>ex2) He lifted it off the floor.<br/><br/>Wouldn't 'onto' make more sense than 'off' in the above sentence?