Yes, I know James Bond movies are not the best place to learn practical physics, but still. In one of Roger Moore`s 007 flicks (I think A VIEW TO A KILL) he escapes the evil minions by breathing the air from a car tire, while underwater.
What would happen if you actually tried this? Would the water pressure be greater than the air prsssure inside the tire and so nothing would come out? Is the air inside a tire breatheable or would it not have enough oxygen to be of any use?
Anyone ever try this? I wouldn`t ask any other group if they had ever been underwater trying to breathe out of a car tire, but hey, this is the Straight Dope crew…
You wouldn’t be able to get more than a few breaths, say two to four, before it was all gone. A typical car tire is inflated to around 30 PSI, but remember that also includes the compression from the expanded tire itself, so there isn’t all that much air in there. It would probably taste nasty, but I’d guess it would be breathable. I wouldn’t recommend it though, especially since the tire may have been inflated with Fix-A-Flat or a similar product and maybe contain toxic gasses. At most, you’d gain a minute or two extra underwater.
A car tire at 35 psi at sea level (1 atmoshpere) should be able to go down to a little over 2 additional atmospheres (29.4 psi, 14.7 psi per atm) and still be able to leak air. 2 atm below the surface is about 66 feet if I remember correctly and am not screwing up my physics. So yes, you could get air from it.
The air in a car tire is just standard air, nitrogen, oxygen, etc., in standard proportions. So it would be breathable.
One of the things they teach in SCUBA is how to breathe if your tank/hoses/anything is leaking air. Yes, you can kind of “breathe” the bubbles if they’re big enough.
So I’d say that yes, this can be done with luck. I wouldn’t want to do it for any period of time though.
I take it you are asking this now, as it was covered in tonights episode of ‘Hollywood Science’ on BBC2. The tyre in question belonged to a Rolls Royce.
They did various experiments (including actually breathing the air from a tyre submerged in a swimming pool), after which they decided it was indeed feasible, but as QED suggests, only good for a few breaths.
Slight sidetrack; the optics of that scene are totally wrong; he is ten yards or so off shore in deep water and he looks almost straight up to see the bad guys standing on the shore (but, oddly, they can’t see him.
I know that light is refracted on entering water, but that scene is ridiculous.
Also don’t forget that air compressors in repair shops don’t have filters on them for removal of oil and other nasty stuff.
As I recall from my SCUBA classes, oil in the lungs would be a bad thing.