So I saw something in a movie yesterday which was too outrageous to really let go of. I won't mention which one, since it doesn't even deserve that.
In any case, after our protagonist had driven his car off of a bridge into the lake, he found himself sinking quickly, and for various plot reasons, he wasn't allowed to be separated from his vehicle. So, obviously, quick thinking chap that he was, he proceeded to release the air in his tires into some duffle bags, which he then proceeded to somehow attach to the car, and no shit managed to float his car to the surface using nothing more than the air from his tires.
I kid you not.
So my first impression, of course, was that if the air were already in the tires, why would the car sink in the first place? Sound thoughts, but maybe we can skirt around that loosely by assuming that the air was pressurized and therefore the lack of volume in expansion prevented buoyancy from kicking in. After all, helium tanks don't float up into the heavens.
But then, as I was considering trying to run the mental math of estimating the air pressure of the tires, their volume, approximate volumes of the bags and the air pressure within them, and so on, I realized that no! I didn't even have to go that far.
The bags clearly had less volume than the interior of the car, and a cabin full of air is incapable of keeping a car afloat, so there is certainly no way that the duffle bags, with less volume, filled with air would be able to float the vehicle upwards. We don't even need to factor in that the water pressure on the duffle bags would have made it even less buoyant than a cabin full of air at normal air pressure.
I won't get into the fact that his window was magically restored after he had kicked it in earlier on in the movie. Or the fact that after being fished out of the lake, he was able to immediately drive off on a high speed chase on what should have been flat tires.
So, feeling vindicated, I then realized that
a. I had seen the Hollywood garbage in the first place and
b. I had turned it into a physics problem.
I lost anyway.
In any case, I think it just went to remind me that every so often I need to expose myself to what passes as American pop culture, just enough to remember why I avoid it so desperately.
In any case, after our protagonist had driven his car off of a bridge into the lake, he found himself sinking quickly, and for various plot reasons, he wasn't allowed to be separated from his vehicle. So, obviously, quick thinking chap that he was, he proceeded to release the air in his tires into some duffle bags, which he then proceeded to somehow attach to the car, and no shit managed to float his car to the surface using nothing more than the air from his tires.
I kid you not.
So my first impression, of course, was that if the air were already in the tires, why would the car sink in the first place? Sound thoughts, but maybe we can skirt around that loosely by assuming that the air was pressurized and therefore the lack of volume in expansion prevented buoyancy from kicking in. After all, helium tanks don't float up into the heavens.
But then, as I was considering trying to run the mental math of estimating the air pressure of the tires, their volume, approximate volumes of the bags and the air pressure within them, and so on, I realized that no! I didn't even have to go that far.
The bags clearly had less volume than the interior of the car, and a cabin full of air is incapable of keeping a car afloat, so there is certainly no way that the duffle bags, with less volume, filled with air would be able to float the vehicle upwards. We don't even need to factor in that the water pressure on the duffle bags would have made it even less buoyant than a cabin full of air at normal air pressure.
I won't get into the fact that his window was magically restored after he had kicked it in earlier on in the movie. Or the fact that after being fished out of the lake, he was able to immediately drive off on a high speed chase on what should have been flat tires.
So, feeling vindicated, I then realized that
a. I had seen the Hollywood garbage in the first place and
b. I had turned it into a physics problem.
I lost anyway.
In any case, I think it just went to remind me that every so often I need to expose myself to what passes as American pop culture, just enough to remember why I avoid it so desperately.
