Kids Riddles

Question: I join you in battle, fist clenched tight.
We pound three times with all our might.
If my rival decides he will sign for peace;
I'll crush him, and the fight will cease.
But if he lays his hand down flat;
I'll suffer defeat, that is that.

What am I?

Question: A semi truck weighing exactly 10,000 pounds gets onto a bridge that is 100 miles long. The bridge's weight limit is exactly 10,000 pounds, any more will break the bridge. After going about 80 miles down the bridge a small bird lands on the truck.

What happens?

Question: I am taken from a mine, and shut up in a wooden case, from which I am never released, and yet I am used by almost everybody.

What am I?

Question: If it's information you seek, come and see me.
If it's pairs of letters you need, I have consecutively three.

Who am I?

Question: If you have a rope around a soccer ball and the moon, which rope would have to increase in length more to create a one meter gap between the rope and the soccer ball/moon?