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A helium balloon is tied to the seat of a car. The doors and windows of the car is closed. If the car now starts moving, in which direction will the balloon move- front or back?

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closed as too localized by David Z Oct 21 '12 at 14:58

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They're talking about the same concept here... –  Waffle's Crazy Peanut Oct 21 '12 at 6:35
right. perhaps illusion has illusively copied the question –  ARITRA Oct 21 '12 at 6:50
@DavidZaslavsky: Hello David. A small doubt... Why was this question closed? My thought is "It's a choice-selection" question. Is that so? –  Waffle's Crazy Peanut Oct 21 '12 at 15:02
@CrazyBuddy ah, sorry, I was in the middle of explaining and I got distracted. It appears to be a homework-like question with no work shown, which goes against our homework policy. Though it's close to being okay; illusion, if you would edit it to say what you've thought about and flag it for moderator attention, it'll probably be fine for reopening. –  David Z Oct 21 '12 at 15:06
Yeah, the link wasn't for you, it was for the OP (I try to always link to the HW policy when closing a question for that reason) –  David Z Oct 21 '12 at 15:20
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1 Answer

up vote 3 down vote accepted

This is a very good question. I intend to do the experiment later.

I think the balloon will move forwards. The heavier molecules of air will tend to remain backwards due to inertia of rest. So it will occupy the place of the lighter helium balloon, making the helium balloon go forwards.

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Just a note that posting complete answers to homework-like questions is a violation of our policy. Ordinarily I would temporarily delete this, but since it's already been seen and accepted there isn't much point, so I'll leave it. –  David Z Oct 21 '12 at 15:08
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