Let's say that you shoot two balls straight up into the air (in vacuum) from the surface of the Earth side by side with one at a higher velocity and the other at a lower velocity. The higher velocity ball will go higher and land later on - of course - than the lower velocity ball. And of course the distance between them will increase. Will the distance between those balls accelerate as they move further from the Earth? Will the distance between those balls continue to accelerate as the lower velocity ball begins to fall back to Earth? Will the distance between those balls continue to accelerate as the higher velocity ball begins to fall back to Earth? My overall question is do the balls appear to accelerate away from each other throughout the entire trajectory?