If an insect is inside of a container, but flying, is it adding weight to the container?
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Mythbusters did an episode called Birds In A Truck exploring this concept and it’s worth a watch for a good ELI5.
As far as I can remember the fly in the box will be pushing downwards with the same force as it’s weight while it’s flying so no matter wether it’s flying or walking the same force of the fly’s weight is pushing down so the box will weigh the same.
Can I ask a follow up.If I make a small hole in the jar, I assume the weight of the container is still increased by the weight of the insect. If I make the hole so big, that the container is just a dish, then I assume the insect flying over the plate adds no weight.
So how big is the hole before this happens? Does it matter where the hole is? Is there an intermediate point where only part of the weight is added to the container?
– Imagine a man standing on a large platform scale weighing himself.
– Now imagine he’s wearing a jet pack while weighing himself.
– Now imagine he turns on that jet pack and flies straight up about 3 feet (or 1 meter) above the platform and hovers there.
Can you see how the downward thrust from the jet pack presses against the scale? That thrust of air has to be just enough to lift the man’s weight off the ground, and the scale will measure that air pressing against itself as the same weight pressing down.
This is just like a fly in a jar using its wings to propel itself upward by forcing air downward toward the bottom of the jar.
I believe yes but a negligible amount with air (version 1) + insect will weigh more than just air (version 2). Air version 1 and 2 are different because assumed it is a closed container, when you open to add an insect to the container, the gas particle concentration changes. Air (version 1) will be less dense, thinner air, less pressure than air (version 2).
A flying insect is also acts as a force. The insect applies a downward force to the air equal to its weight. In a closed container, that air cannot escape, so its motion supplies a downward force to the container that is exactly the same as the weight of the fly.
Now, the apparent weight of the total weight of container will fluctuate slightly as the insect accelerates and decelerates or initiates flying, but the fluctuations will always be around the weight of the insect.
If the container isn’t sealed, then the air can escape into the environment without transferring its full downward force to the cage. The total weight will be lighter when the insect is flying in an open container.
Weight is equal to Mass multiplied by the strength of gravity.
The mass of an object is constant regardless and for the purposes of this example, the gravitational pull on these objects is also constant. Therefore, the weight of both the jar and the fly do not change.
With that in hand, the question becomes “is the combined weight of the jar and fly equal more than the jar itself” to which the answer is obviously yes since the fly’s weight cannot be zero.
A flying/buoyant object does add to overall weight however, it spreads that weight over a wider area that can be difficult to measure. For example, a balloon full of Helium still has weight but it’s almost impossible to measure practically.
I won’t get into the technical difference between weight and mass and how that changes this question significantly. It’s awfully pedantic and I don’t want to be the one to open that jar of flies.
Just think of it like this: the insect’s body is resting on the air that rests on the container floor.
Remember that air is a fluid… If the container was full of water, and the insect was a fish… would it not add weight? If that seems difficult to imagine, scale it up. Replace the container with a large swimming pool, and the fish with a with a whale… Just as a fish or whale seem to be “floating” in water, an insect seems to “float” on air… But really they aren’t “floating” at all, they are supported by the water or air itself, which is no different than when you are sitting on a stool… If you pick your feet up and don’t touch the ground it doesn’t mean you don’t weigh anything… It just means all your weight has been transferred to the legs of the stool.
Yes. The insect is taking up space that would otherwise be occupied by air. It displaces this air when it is inside the box.
While an insect hovering in a closed box, presumably filled with air, would be displacing air (and therefore applying its displaced weight downwards), wouldn’t the measured weight still be less than on account that you’d be increasing air pressure in the closed system, which would press equally on all sides of the container? Its mass would be the same as if it were sitting, but actually weighing it would give a middling value.
Am I right?
Maybe that depends more on whether the container itself can flex, or is completely rigid.
A few other people here have done good jobs explaining, but if I was truly talking to a 5 year old, I’d say something like this:
Yes. When a bug (or a plane, bird, or whatever) is flying, it isn’t making itself weigh less. It’s pushing down on the air around it, which pushes down on the ground, to lift itself up in the opposite direction–just like you push down on the arm of a chair or table to help you stand up.
If that air is inside a box, it will push down on the box to lift the bug up a (roughly) equal amount to that bug’s weight. The box will weigh the same as if the bug was sitting down.
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