Good Riddles

Question: What is as big as you are and yet does not weigh anything?

Question: What do you call 2 Us?

Question: My name is Ruger. I live in a farm. There are four other dogs in the farm with me. Their names are Snowy, Flash, Speed, and Brownie. Who is the fifth dog?

Question: In the harbor of a small town, there is a large boat. Coming off of the boat is a ladder reaching down so that the bottom rung is just above the surface of the water. As the tide comes in, the water rises at 1 foot every 30 minutes, and continues like this for 3 hours. If the rungs are each 1 foot apart, how many rungs are under water when the tide stops rising?

Question: Without me, nothing exists. What am I?