You work for a balloon delivery service and you are delivering a single, helium-filled balloon in your car. To prevent the balloon from bouncing around on the ceiling while you are driving you have tied a string with a weight on it to the balloon. The weight is resting on the floor and the balloon is floating just below the ceiling.

When you accelerate, does the balloon stay where it is, move backward, or move forward? What does it do when you make a turn?

Assume all the windows are closed and the vents are turned off so there is no air flow inside the car to affect the balloon.

the solution poses fair resoning to defend its stance... however, it is not plausible to come to this conclusion when you neglect the inertia of the air directly infront of the balloon.  as this air accelerates toward the back of the truck, it will push the backward on the balloon, and counteract with equal or greater force on the balloon than the air behind the balloon, which is expected to have a very very slighty greater density(and pressure) than the air in front, and 'push' the balloon.

because the density of the air on either side of the balloon differs by such a miniscule, and immeasureable amount, the balloon will have an inertia almost as if there is no air in the truck... therefore the balloon will move backward!

Posted by Jud on 2005-08-11 13:26:52