An empty balloon (or a soft plastic bag) weighs the same as what it does when filled with air at atmospheric pressure-explain why.

Explanation

An empty balloon or a soft plastic bag displaces a very small quantity of air. The balloon gets inflated when filled with air at atmospheric pressure and displaces a larger amount of air. More the amount of air inserted into the balloon, the larger the volume of air displaced by it. Hence, the increase in weight of the inflated balloon due to the inclusion of air into it becomes just equal to the apparent decrease in the weight of the balloon due to the displaced air. For this reason, an empty balloon (or a plastic bag) weights the same as what it does when filled with ait at atmospheric pressure.