if you drop a permanent magnet, it becomes less magnetic.Why?

It's pretty unlikely, but not impossible, that you could bump a piece of iron and make it a magnet. To bump a piece of iron and turn it into a magnet you would have to bump it in such a way that a perfect vibration travels through the material. The reason that would be hard to bump a piece of iron and make it magnetic is because of the way vibrations propagate in the material. Vibrations radiate out from the point of impact and are going at different angles relative to a straight line - the line you would like the domains to line up with. Non-uniformities that exist in all materials also change the flow of the vibrations in a material