When an acrobat walks on a tightrope, she extends her arms straight out from the sides. She does this to make it easier for her to catch herself if she should tip from one side to the other. Explain how this works.

Question

Maybe something with center of mass? This is one that just seems intuitive but is hard for me to explain...

Answer 1

Actually, many of them carry a long pole from side to side.
Without arms extended, the moment of inertia about the feed is much less than if the arms and pole are held highter. The cm is displaced much higher, and more importantly, the center of interial is lengthened.

moment of inertia about the feed if all the mass were in center mass, at a height of L from the feet: ML^2. Notice what happens when L is lengthend.