Good Riddles

Question: If a man carried my burden, he'd break his back.
I am not rich, but I always leave silver in my track.

What am I?

Question: You bury me when I'm alive,
and dig me up only when I die.

What am I?

Question: Why does the second shape have an open block when the first shape does not?

Question: I fasten to walk,
and unfasten to stop.

What am I?

Question: 7 frogs are sitting on a log. 1 of them decides to jump off of the log. At this moment how many frogs are on the log?