If a cup full of water is dropped from the top of a tall building and falls freely, several things will happen to the water in the cup due to the effects of gravity and air resistance.
As the cup falls, both the cup and the water inside will experience the same gravitational acceleration. Initially, the water will remain in the cup due to inertia, as there is no external force acting on it. However, as the cup accelerates downward, the water will also accelerate. The cup and the water will effectively be in free fall together.
When the cup is in free fall, the effects of gravity are cancelled out within the falling frame of reference. As a result, the water will float freely inside the cup, just as if it were in zero gravity. It will appear to be weightless and will not settle at the bottom of the cup.
However, the presence of air resistance can have an impact. As the cup accelerates downward, it will encounter air resistance that opposes its motion. This resistance can cause the cup to experience drag, and as a result, the cup and the water inside will experience a relative motion due to the differential drag forces acting on them.
The water in the cup may slosh around and form waves or ripples as the cup falls. If the cup is open at the top, there is a possibility that some water may splash out due to the motion and disturbances caused by air resistance. The shape of the cup and the speed of the fall will influence the extent of these effects.
In summary, while the water will not settle at the bottom of the cup due to the free fall, the presence of air resistance can cause the water to move and potentially splash out, leading to a dynamic and turbulent behavior.