In 1654 Otto von Guericke, inventor of the air pump, gave a demonstration before
ID: 2263902 • Letter: I
Question
In 1654 Otto von Guericke, inventor of the air pump, gave a demonstration before the noblemen of the Holy Roman Empire in which two teams of eight horses could not pull apart two evacuated brass hemispheres. Assume that the hemispheres have thin walls, so that R in the figure may be considered both the inside and outside radius. Taking R as 42 cm, the inside pressure as 0.067 atm, and the outside pressure as 1.0 atm, find the force magnitude the teams of horses would have had to exert to pull apart the hemispheres.
In 1654 Otto von Guericke, inventor of the air pump, gave a demonstration before the noblemen of the Holy Roman Empire in which two teams of eight horses could not pull apart two evacuated brass hemispheres. Assume that the hemispheres have thin walls, so that R in the figure may be considered both the inside and outside radius. Taking R as 42 cm, the inside pressure as 0.067 atm, and the outside pressure as 1.0 atm, find the force magnitude the teams of horses would have had to exert to pull apart the hemispheres.Explanation / Answer
Net pressure = 1 - 0.067 = 0.933 atm
1 atm = 101325 Pa
Thus net pressure = 0.933*101325 = 94536.2 Pa
Cross-secton Area A = 3.14*R^2 = 3.14*0.42^2 = 0.5539 m^2
Force = pressure *area
= 94536.2*0.5539
= 52363.2 N