Suppose you wake up one morning go outside and notice that a

Suppose you wake up one morning, go outside, and notice that a tire on your car is completely flat. You have a pressure gauge, with which you verify that the pressure is indeed zero. Do you then deduce that the flat tire is a perfect vaccum?

Solution

The flat tyre is indeed not a perfect vaccume or even a vaccum ; for this we have to understand what the reading in the pressure guage shows ; the pressure guage show the pressure difference between the air inside the tyre and out side the tyre; if the guage show zero difference , it mean the pressure outside of the tyre is same as the pressure inside the tyre, which concludes there is some air in the tyre and the pressure is 1 atm same as out side.

we know that out side of the tyre the air in the atmosphere on ground is at a pressure of 1 atm , so the same pressure is also maintained in side the tyre .

if we consider a ballon which is enclosed at room pressure , we can inflate the ballon by decreasing the out side pressure or incresing the inside pressure by blowing the air.