I envision it like this.
Let’s take a tall box. Ten foot tall cardboard box. Now, let’s put a ten pound rock inside. Seal up the box.
Now, take the box and heave it upward, but don’t let go of the box.
The rock flies upward and is no longer weighing the box down. In those moments while it’s in the air, does that 10 pound rock add weight to the box?
By the use of magic, we turn the 10 pound rock into a fly in mid-air. Now, it’s flying around inside the tall box and it’s not resting. Mid-air, all the time. Does the fly add weight to the box?
Yes, it doesn’t matter what the fly is doing in there, as long as it’sstationary. If it’s flying, a scale would read that the jar is heavier by the weight of the fly because the fly is pushing air down with the same force that gravity is pulling it down.
If the fly is actively flying upwards then the scale would read a little more, for the same reason that a scale reads more when you’re crouched down and start to jump up.
Yes, because to fly it must exert a downward force on the air in the jar – which is ultimately transmitted to the world outside the jar through the jar itself. It could momentarily not exert a force if it stops trying to create lift, but it would fall and then briefly exert a stronger force on landing.
If it’s a closed container then yes (I think). It might depend on how you define the mass and small temporary fluctuations may happen.
For something to fly it must exert a force equal or greater than its weight downwards. This force comes from the wings of the insect acting on the air, i.e. exerting a force on the air. This force is downwards and therefore the air exerts a force on the ground. Any scales under the container will see this force as a weight/mass.
It gets trickier if the insect flies to the top then free falls. When free falling there isn’t any force being exacted by the insect, so the scales wouldn’t detect it.
For the sake of clarity there is a difference between weight and mass of a system, and what you think is measuring mass is almost certainly measuring voltage, which is linked to weight, which is linked to mass. So there is a bit of separation.
In almost all scenarios weight and mass are essentially the same thing, but not always and especially not when using measuring devices with some degree of separation.
The mass of a closed system is constant. You just might not be able to measure it as constant due to limitations in measurement techniques.
When something flies, the air is used to lift the object and the air itself receives a reaction force equal to the object lift. In this case the fly is resting it’s weight on the air that exerts that weight to the container. The weight of the system is the same as if the guy was resting on the floor.
To solve this problem do this next time: is the action exert forces or transfers energy or mass outside the system? If no, the energy, the mass and the total of forces in the systems are the same between the 2 scenarios.
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