Answer:
I am lighter than air but a hundred people cannot lift me. Careful! I am fragile!
I have feet on my head
I can run but not walk. Wherever I go, thought follows close behind. What am I?
I am all around, yet to me you are half blind. Sunlight makes me invisible and difficult to find. What am I?
I am an instrument that you can hear but cannot see or touch. What am I?
What did the piece of wood say when he saw the screwdriver and screws approaching?