I’m not the same person, but it seems like you’re right. Pound (lb) is a unit for measuring mass. The same is true for kilogram. This actually surprises me to some degree, since it had not been clarified like this to me earlier:
In common usage, the mass of an object is often referred to as its weight, though these are in fact different concepts and quantities. Nevertheless, one object will always weigh more than another with less mass if both are subject to the same gravity (i.e. the same gravitational field strength).
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Because mass and weight are separate quantities, they have different units of measure. In the International System of Units (SI), the kilogram is the basic unit of mass, and the newton is the basic unit of force. The non-SI kilogram-force is also a unit of force typically used in the measure of weight. Similarly, the avoirdupois pound, used in both the Imperial system and U.S. customary units, is a unit of mass, and its related unit of force is the pound-force.
Source: Wikipedia: Mass versus weight
I think we’re probably confused of this because in common usage, we’ll ask “how much does it weigh” and expect to get an answer in the unit of mass instead of force, just because the mass of the object defines the amount of force it will have in some given gravity condition.
Insert the end of a cutlery knife between the rim of the glass jar and lid from below. Give it a tiny wiggle, and the jar will pop open. At least if it’s stuck because of a vacuum.
If that didn’t work, poke a tiny hole in the lid with a sharp object to break the vacuum, but please be careful if using a kitchen knife for this! A nail or a screw is probably a safer choice.