Brainteaser: Balloon on a Bus

(Image credit: Flickr user Frank Wuestefeld)

You're sitting on a bus. The kid next to you has a helium-filled balloon and it ends up against the ceiling, just about in the center of the bus. The driver suddenly hits the gas pedal and the bus lurches forward, throwing you back into your seat. What does the balloon do?

a. It moves backwards.
b. It moves forward.
c. It stays where it is.

Continue reading for the correct answer.

The answer is (highlight): b. It moves forward. When the bus moves forward, the heavier air moves to the back of the bus. The helium balloon is lighter than air, so it is pushed forward. Give it try yourself sometime!


This brainteaser was reprinted with permission from Uncle John's Unstoppable Bathroom Reader.


Newest 5
Newest 5 Comments

Relative to the bus, I would assume it appears to lurch "backwards" since we are connected to the moving bus, and the balloon is relatively free. Would this be relative acceleration towards the back of the bus? Let's go look at the answer.
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