Scenario on Angles

My dad is in his 50s but he has a cow, So he made a pen and place a iron bar in the middle of the pen and tie the cow on it. He extend the rope so that the cow can move freely around so he would not have to move the cow every two days again because it can move freely around the pen to get feeding/grass to eat.

What do you understand from this scenario?

Did the iron bar move when the cow goes around the pen?

So if the cow move from one point to another without the iron bar moving what is formed?