If two identical balls are connected to the same very long rope, and one of the balls are floating in space and the other one is hanging above earth’s surface. What would happen?

Question

So my 7-year old asked me this and as much as I would love to be able to give him a proper answer, I couldn’t.

Does ball A (in space) float away, taking ball B (above earth’s surface) with it? Will the balls stay somewhat fixed or will ball B force ball A down?

In: Physics

Answer 1

Assuming that “floating” means in orbit (otherwise, they just fall), they are “balanced” around the center of mass of the balls (half-way down the rope). One ball pulls “up”, and the other “down”, keeping the rope under tension. Congratulations – your 7 year old has intuited tides.