Logic Riddles

Question: You have bag, you put a lump of metal into the bag, then you put a lama into the bag, then you put something else into the bag, and yet the bag weighs nothing. Why?

Question: in all of written history I won't show up at the end of a sentence but I will be there in the end . . .

Question: What comes down and never goes up?

Question: At work a lady is requested to move a 2 ton machine with out any assist.How is she able to move the item?

Question: I can pogo on the moon, but not Mars. I can pogo on this table, but not on a stick. What can assure us to be able to pogo on objects at all times?