sandbag
The balloon initial speed is 10m/s; meanwhile, the sandbag while is still in the balloon, has the same speed of 10m/s; at that point, we can think of the balloon and the sandbag as one object. If for instance the sandbag has been dropped from the balloon, those standing in the balloon would feel the sandbag going straight downward with an initial speed 0m/s because in fact the relative speed of the sandbag to them is 0m/s. Furthermore, at the first moment of drop taking place (the first moment of the sandbag is in the air), the sandbag is on its own with no fed upward speed from the balloon. At that very moment those in the balloon are continuing of traveling upward with the speed of 10m/s watching the sandbag getting more distant from them. In fact, this perception would happen only to those standing inside the balloon.
On the other hand, for those who are watching the balloon from distance (from a spectator point of view) would see the sandbag traveling with the same balloon speed at 10m/s for some fraction of time (initial speed) after it has been dropped. Then immediately after the dropping took place, the sandbag would start decelerating its “initial speed” of 10m/s. Decelerating its initial speed? Yes, then it’s still traveling upward since it has a speed. An object in motion continues to travel with constant velocity unless acted on by an external force – Newton first law. So, what external force is acting on the sandbag to change its continues traveling with its initial speed (regardless to outside factors like air resistance)? Mass of course. At that moment a battle is taking place between the mass of the sandbag (decelerating it and pulling it downward) and its velocity (pulling it upward). The moment the mass wins – speed is 0m/s; a fall would take place. For sure the middle picture is the correct one from an experimental point of view.
I was thinking of another example that may describe, with a certain similarity, the same situation. Once I was sitting next to my friend who was driving a car. At that point I wasn’t looking at the speedometer, but let's just assume it was 50km/h. We were lazy to stop the car next to a trash container, so I could drop my soda can. So why not shifting the car’s direction to get closer to the container and throw the can without stopping the car my friend says, and that exactly what happened. The car starts taking the right lane direction long ago before reaching the container, and then I threw the can out of the window when the container appeared. What happened is the can, unlike what I assumed would happen, not only missed the container but also kept traveling a certain distance on the ground. Another example is warplanes bombs. Warplanes have to release their bombs before the plane reaches its target. Like in the World War II when the cam is recording the falling bombs from inside the plane ground hole, you can still see the bombs traveling with the plane for a certain time after their release. One more example is the space rocket. At a certain point of traveling the space rockets has to release its lower part. Those sitting in the space rocket for instant would see the lower part of the rocket falling instantly at an initial speed 0m/s. Meanwhile, when the event is broadcasted on TV, we can clearly notice that the lower part would keep rising upward following the space rocket before finally starting to fall, and that exactly what happened in the balloon and the sandbag.
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Is it more complete now or is there still something I missed?
I would like to thank you all for your guidance.
