Bee in a jar

1. Sep 14, 2007

lalaland123

A bee is flying in a closed jar. The jar is dropped. What happens to the bee while the jar is falling??

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please explain this in simple language... i'm in high school..

2. Sep 14, 2007

Loren Booda

Something like what happens in between your flying above earth - before, during and after - Earth's screeching to a halt. (Air imparts a gradual transfer of acceleration.)

3. Sep 14, 2007

lalaland123

sorry, i didn't really understand that..

my question is: while the jar is fallng, will the bee remain where it is or will it hit the lid of the jar?

4. Sep 14, 2007

Loren Booda

I don't want just to give you the answer to the problem, but here are some hints:

What do you think would happen if there were no air in the jar (assuming the poor bee held its breath)?

What do you think would happen if the bee were suspended in a jar full of water (and the bee is likewise holding its breath)?

The answer to your question, elucidated in Galileo's experiments, is somewhere between these two situations.

5. Sep 14, 2007

Shooting Star

The presence of air in a closed jar is of no concern actually, if we assume no air outside.

As a first approximation, lets assume that the earth has no atmosphere, so as to neglect air resistance. Also, that the jar is small compared to the earth, and it falls for a short distance, so that the gravitational field is essentially uniform, which means that acceleration due to gravity is always in the same direction, i.e., downward, and the magnitude is constant.

Then the falling jar, because every particle of matter is being accelerated at the same rate, behaves like a frame where there is no gravity. This means that any body inside the jar (or outside, for that matter), which is falling due to gravity only, behaves as if there is no force acting on it. Any particle inside the jar, which was static with respect to the jar at the moment the jar started to fall, will remain static wrt the jar. The effective gravity inside the jar is zero.

About the bee: Flying in zero gravity may not be possible for the bee. Flying is essentially a process that takes place when there is gravity. But if the bee keeps still, it will just remain there and not touch the lid.

Introducing air resistance will slow down the falling of the jar, and there will an effective g-field inside the jar, but I think what you had wanted to know is not about this case.

6. Sep 14, 2007

tabchouri

I think that the definition of the problem is different.
The jar was dropped, as i understand it, it was held againt gravity. And thus, the bee was flying against gravity.
So when the jar is dropped, it starts to accelerate down. The bee, which is still counter acting gravity (holding itself in non gravitational state), will touch the lid.
Unless the bee stops flying the moment the jar is dropped that is (in which case it will remain at the same position compared to the jar).

Last edited: Sep 14, 2007
7. Sep 14, 2007

Shooting Star

Dear tabchouri, I was just trying to elucidate the essence of the problem to a high school student. Why confuse him further?

8. Sep 14, 2007

Staff: Mentor

9. Sep 14, 2007

Shooting Star

Without googling it, the "vomit comet" was first used by NASA to simulate weightlessness. NASA called it the Weightless Wonder. Nowadays, others use this concept to make movies and do other research.

It's a plane that dives down in a parabolic trajectory such that the acceleration is exactly g downwards, and so there is no effective gravity inside. It has to expend power to maintain this accleration of g because of air resistance. It can do this for about 20-30 seconds only, otherwise it'll crash. Then it has to climb out the dive very fast, resulting in high g forces inside the plane.

10. Sep 14, 2007

Loren Booda

Remember that the bee falls more like a feather (yet still does accelerate somewhat in its airy environment) than the jar, which falls essentially without friction for this experiment.

11. Sep 14, 2007

AlephZero

A bee flying in a vacuum is an interesting concept (unless it's a rocket-propelled bee or something).

Don't simplify the OP's problem TOO much, otherwise it turns into a different problem!

12. Sep 14, 2007

rcgldr

The bee would probably react as if it hit a sudden updraft (thermal), and after a short initial rise would relax and hold it's slightly higher position.

13. Sep 14, 2007

Shooting Star

Let's all just stay focussed on the original problem. Is the flying bee complicating matters?

Let's just consider a feather which was "floating" in the jar, that is to say, it was stationary with respect to the jar. Then the whole system was allowed to fall in absence of air. I think, in essence, this is what the OP was all about. Remember that it's a high school problem.

In this case, the feather will remain in the same position with respect to the jar. It will not touch the lid. There is no acceleration of the feather with respect to the jar. The whole system is in free fall in uniform gravity.

The difficulty with the flying bee is that it will not be able to "fly" in the usual sense of the word once the jar is released and is in free fall without air resistance. Yet if it continues to move its wings, who knows where it’ll land up?

Dear lalaland123, have you been able to make anything out of all this?

14. Sep 14, 2007

Paul H

I think it depends on how far the jar falls,

1. Short drop--bee is flying, jar is dropped, jar accelerates downward before the bee realizes it and gets hit on the head with the inside of the jar lid, jar hits the ground killing the bee.

2. long drop--(same as above except) but this time the jar continues to fall, bee regains control and braces it's self for the impending impact, eventually the jar hits the ground, jar breaks open and the bee flys away.

So the real question is whether the bee is 1. dead OR alive, 2. dead AND alive. 3. neither dead nor alive.

15. Sep 14, 2007

Shooting Star

1. Short drop: What do you mean by the jar accelerates before the bee realizes it? The bee is also accelerating at the same rate! There’s no question of the bee realizing and voluntarily participating in the fall! The bee, if it’s stationary inside the jar, does not get hit on the head. If the jar hits the ground, then getting hit by the ground may or may not kill the bee!

2. Long drop: Bee cannot regain control because it has never flown in zero gravity and does not know how to do so. It’s brain and body is not designed to fly in zero gravity. That’s why I said who knows where it’ll land up. And does it know that it’s going to hit the ground, so that it’ll brace for the impact? And why should it fly away this time, instead of hitting the ground hard and getting squashed?

Focus, Paul, focus. Let’s not keep on introducing unnecessary, irrelevant variables into the thought expt. Now somebody will ask if it’s an African killer bee or the European variety!

16. Sep 14, 2007

tabchouri

Well, i guess there was some ambiguities in the problem's definitions, else there wouldn't have been so many replies with different assumptions and scenarios.
I think we all had to deal with adding some assumption in order to have a reply for a well defined question : is this an academic example to illustrate that every object accelerates the same way in a same gravity ? or is it really a problem of a bee flying (exerting force to counter act gravity) ?

In some ways, all the answears are valid considering the assumption made to infer them.

I'm sure it would have been much more easier and obvious if it was just a feather or a little ball instead of a bee ...

Last edited: Sep 14, 2007
17. Sep 14, 2007

Paul H

1. the bee is maintaing it's flight relative to the jar wall when the jar is dropped the be does not start to drop at the same time as the jar (lag time)
2. I never said that the bee would fly in the free fall, as for getting squashed that was the #1 result.

18. Sep 14, 2007

Paul H

I understood the question, I was just poking fun at the cat in the box paradox,
How about some practical experimentation, I will catch a,, humm how about a fly (I can catch one of those) and let you know what happens.

19. Sep 15, 2007

Shooting Star

You are very true. But I had from the start asumed that it was an example to illustrate that every object accelerates the same way in a same gravity.

This bee is one in the bonnet...

20. Sep 15, 2007

Shooting Star

Hey, I got the joke, but my concern was about the high school student who had wanted some clarification in the first place.

Instead of Schrodinger's cat paradox, let's consider the other one -- Schwinger's friend. We can put you in the jar and drop you...