Normal atmospheric pressure is \(1 \mathrm{~atm}=\) \(760 \mathrm{~mm}
\mathrm{Hg} .\) However, it is also \(14.7 \mathrm{lbs} / \mathrm{in.}^{2}\)
(14.7 pounds per square inch). Given that liquid mercury has a density of
\(13.6 \mathrm{~g} / \mathrm{mL}\), explain (show a calculation) why \(1
\mathrm{~atm}\) also equals \(14.7 \mathrm{lbs} / \mathrm{in}^{2}\). Then, go
back to the introduction of this chapter and calculate that the atmospheric
force holding the Magdeburg spheres together is indeed close to the stated
\(4.5\) tons (the surface area of a sphere is given by \(4 \pi r^{2}\) ).