On the moon, we are taught at school that two balloons, one filled with air and one filled with concrete, would drop at the same rate. However, on Earth, they obviously don't, with the concrete falling faster. Our reasoning is that air resistance is not a factor in this example, so the only other variable is the mass (density) of the two balloons. If you were to change the medium from Earth's atmospheric air to water, the air balloon floats as it is less dense than water and therefore displaces more water than its mass, resulting in an upwards buoyancy force acting on it. The concrete sinks for the same reasons. Therefore, in the medium of air, there is also a somewhat reduced buoyancy effect acting on the balloons, explaining why the concrete balloon falls faster. Can someone please confirm if our logic is correct, and if not, explain what other forces are playing their part?