How to remove the attached source which was added to a Jar?

Why is it so difficult to remove the lid from a vacuum sealed jar?

• Why is it so difficult to remove the lid from a vacuum sealed jar? in terms of the motion of the air molecules outside the jar. it is also helpful to consider this against the non ...show more

• Answer:

  Consider this. Atmospheric pressure is about 14.7 psi at sea level. An ordinary glass jar lid is about A = pi r^2 = p()*1.5^2 = 7 in^2 in area. So that can lid you're trying to open has F = 7*14.7 = 102.9 lbs of force acting on it to keep it on the jar. We assume a perfect vacuum. With something less than that, there would be less than 103 lbs, but still quite high. And that's why the lid of a glass jar is hard to remove; there's lots of force from the atmosphere acting to keep it on until you break the seal and let air in. And then the forces inside and outside the lid are the same; so there is no net force to keep the lid on.