Answer:
My tongue hangs out as I run over fields and streets all day. I get tied up every morning and untied at night.
Tall in the morning, short at noon, gone at night. But I'll be back soon.
An iron horse with a flaxen tail. The faster the horse runs, the shorter his tail becomes.
You will find me with four legs, but no hair. People ride me for hours, but I don't go anywhere without needing to be tugged. Jerked or turned on, I always manage to be ready for work.
My life can be measured in hours. I serve by being devoured. Thin, I am quick. Fat, I am slow. Wind is my foe.
You kick me, you punch me, and you beat me up all class. When you leave, you don't even say thanks for allowing you to beat me up. What am I?