nomme Posted November 26, 2003 Share Posted November 26, 2003 A helium filled balloon is tethered inside a car such that it floats at the top of a piece of string, without touching the car's ceiling. All windows are shut and the car is driving along at a steady pace. The driver suddenly brakes to a stop. Relative to the car, does the balloon a) move forwards, b) move backwards, c) stay in the same position as the car decelerates? ....and why? Nomme Link to comment Share on other sites More sharing options...
Hodge Posted November 26, 2003 Share Posted November 26, 2003 None of the above - it would be deflated on the floor, as, being the big kid that I am, I would have inhaled the helium for a moment of amusement caused by the temporary high pitch of my voice, long before the journey even started. I'm even sat here laughing at the thought of it, getting strange looks from others in the office. Link to comment Share on other sites More sharing options...
Hodge Posted November 26, 2003 Share Posted November 26, 2003 OK, I do actually know this one, but don't want to post the answer and ruin it for anyone else. It's quite interesting though. Link to comment Share on other sites More sharing options...
hiyabeing Posted November 26, 2003 Share Posted November 26, 2003 I guess A, but don't know why. And Hodges (?) - you made me laught too - luckily no one else here at the moment. Link to comment Share on other sites More sharing options...
Moonolt Posted November 26, 2003 Share Posted November 26, 2003 It'd have to be C, surely!... maybe not. Link to comment Share on other sites More sharing options...
Sidla Posted November 26, 2003 Share Posted November 26, 2003 Surely it has to be C. If it's tethered to the car then it must be moving the same speed as the car and the air in the car. The more I think about this though, the more I think it's wrong. Link to comment Share on other sites More sharing options...
upholder Posted November 26, 2003 Share Posted November 26, 2003 I would say A. Why? The balloon has very little mass thus very little inertia so the car coming to a sudden halt wouldn't affect the balloons motion (relative to the car) much at all. However the balloon is tethered by a piece of string which has mass, therefore inertia so when the driver suddenly brakes to a stop the string moves forward pulling the balloon with it. Link to comment Share on other sites More sharing options...
Jamie Posted November 26, 2003 Share Posted November 26, 2003 I'd say backwards ... because the balloon had less density than the surrounding air ... Link to comment Share on other sites More sharing options...
ROBERT Posted November 26, 2003 Share Posted November 26, 2003 Does the car have a sunroof? If so is that open? And the driver that suddenly brakes to a stop- is he in the same car as the balloon? Link to comment Share on other sites More sharing options...
Funke88 Posted November 27, 2003 Share Posted November 27, 2003 C: Stay in the same position. The air inside the car is not moving. The balloon is not attached or touching anything so therefore cannot be affected by the movement of the vehicle or any outside forces like the wind. It cannot experience g-force as it is not in contact with any part of the car. Thats my theory and I'm sticking to it. Probably wrong but I did think it through. I feel like I'm back at school. Link to comment Share on other sites More sharing options...
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