About a bee flying inside a moving train

[fujiwara_sai]

I have some questions which i can't seem to answer and understand. Here goes:
Imagine a bee flying inside a moving train moving at a constant velocity in one particular direction. the bee is flying in mid-air and is not in contact with any of the train parts.

qns 1: does the bee need to continously flap its wings(so to speak) to fly forward in other to maintain in the same position?

qns 2: is there any difference when the frame of references are one inside the train and one outside the train.

qns 3: what will happen if the train accelerates? i feel that in this case, the bee will have to exhaust energy to fly forward in order to maintain in the same position but i am not sure and doesn't know to explain it.

thanks a million for helping me out with this question.

 

[anantchowdhary]

qns 1: does the bee need to continously flap its wings(so to speak) to fly forward in other to maintain in the same position?

No the bee doesn't need to flap its wings to fly forward to maintain the same position.

qns 2: is there any difference when the frame of references are one inside the train and one outside the train.

Yes ofcourse there is...the person viewing from outside thinks that the bee is moving...whereas the person inside the train thinks the bee is stationary

 

[Maxwells Demon]

everything inside the train is going the same speed as the train, even the bee.. You don't feel the air from inside the train blowing in your face in the train, it is also moving.. In the same way the bee is also moving even though it hasn't contact with any solid materials...

so like anantchowdhary said: the bee doesn't need to flap its wings to fly forward to maintain the same position.

 

[out of whack]

Yes ofcourse there is...the person viewing from outside thinks that the bee is moving...whereas the person inside the train thinks the bee is stationary

I think the second question is asking if there is a difference not in the point of view but in the force needed to keep the bee moving when you see it from outside the train. Seen from inside the train, the bee is stationary. Seen from the outside, it has a uniform linear motion. In neither case do you need to apply a force to keep it that way.

 

[out of whack]

Oh, and for question 3, if the speed of the train ceases to match the speed of the bee then the bee will appear to be accelerating in the opposite direction when seen from the inside. It can counter this apparent acceleration by applying a force (using its wings). Seen from the outside, the bee will need to accelerate to match the train speed by applying that same force.

 

[denverdoc]

just so long as we all agree that the bee better be flapping something to stay aloft!

 

[HallsofIvy]

Anantchowdhary and Maxwellsdemon don't seem to think that! Perhaps they could explain what is going to keep the bee aloft.

 

[anantchowdhary]

hehe...i think the question was as follows:
qns 1: does the bee need to continously flap its wings(so to speak) to fly forward in other to maintain in the same position?

...so i really think its about linear motion...Therefore i gave my answer

 

[Maxwells Demon]

I agree with all of you. I guess I was just bad at telling you in the right way :)

 

[anantchowdhary]

I agree with all of you. I guess I was just bad at telling you in the right way :)

Could u pls elaborate??are we correct or not??

 

[denverdoc]

I was just trying to add a little "levity" If it were an ant, non-flying variety, no problem.

If you'll forgive an aside, reminds me of the balloon in a car collision problem that came up recently--suppose a helium balloon is tied to the gearshift of your souped up sport input which due to your inattention, hits a brick wall at 60MPH, in which direction does the balloon first travel?

 

[Maxwells Demon]

we are correct

 

[DaveC426913]

'About a Bee' - isn't that a Hugh Grant Movie?

 

[out of whack]

suppose a helium balloon is tied to the gearshift of your souped up sport input which due to your inattention, hits a brick wall at 60MPH, in which direction does the balloon first travel?

Opposite to the pendulum that was suspended above it. Actually, both would continue in the original direction of the car except that, being tied to a string, the balloon would also accelerate downward and the pendulum would accelerate upward. Did I get it?

 

[DaveC426913]

The key to understanding this question is to recognize that the bee interacts directly with (and thus all its motion is referenced to ) the volume of air in the train - and deos not intreract with the train itself or the outsdie world. Ask first what effect the train's movement has on the air. Once you know that, ignore the train and ask what the bee does wrt the air it is flying through.

 

[DaveC426913]

Opposite to the pendulum that was suspended above it. Actually, both would continue in the original direction of the car except that, being tied to a string, the balloon would also accelerate downward and the pendulum would accelerate upward. Did I get it?

No. The key to understanding balloon behaviour is to understand the behaviour of the air around it.

The sum total of the mass - and thus interia - in the balloon and all its helium is LESS than the sum total of the same volume of air that the balloon is displacing. So the air in the car continues forward with greater enthusiasm (read: inertia) than the helium balloon. Thus, balloon strains backward upon impact.

Another way to understand it is to think of a helium ballonn as - not an object - but as a small bubble of low vacuum in the air. It's the air that acts, not the bubble of vacuum.

 

[out of whack]

So the air in the car continues forward with greater enthusiasm (read: inertia) than the helium balloon. Thus, balloon strains backward upon impact.

Ah, got me. Nice one!

 

[anantchowdhary]

Suppose we perform the experiment in vacuum...if there was some way to keep the bee aloft...Would the bee then also stay in the same position even if the train moves??

 

[denverdoc]

Nope. no reason i can think of.

 

[anantchowdhary]

thnx

 

[fujiwara_sai]

thanks a million for the numerous replies, i finally begin to understand it and i even learned a new concept with the balloon in the car

and...also sorry for the inconvenience caused by posting it in the wrong section intially and has it to be moved to the correct section

 

[f(x)]

what if the speed of the train is close to speed of light ?

 

[Ahmed Abdullah]

I think If such a thing happens, the train will not exist. The mass of the train will be transformed to energy (that is wave particle duality). Am I right?

 

[anantchowdhary]

nop...how d u think the mass will transformed into energy??

 

[f(x)]

I think If such a thing happens, the train will not exist. The mass of the train will be transformed to energy (that is wave particle duality). Am I right?

The moving mass will be different from the rest mass but that's not the matter of concern...
I was asking pertaining to relativistic terms, specially the frames of reference, both inside and out of the train

 

[anantchowdhary]

if the speed of the train is close to that of light...then the bee would be going back but you would observe it in slow motion..

 

[denverdoc]

Almost right, there is certainly time dilation present, but unfortunately the benefits accrue to the occupants of this silver bullet. The twin paradox where the sedentary twin sends his space cadet bro off at near light speed grows old and dies between his twins need to shave. This is a good thing as it is the only known possible rescue from our ever knowing the universe w/o wormholes or greater than C velocities.