In 1656, the Burgmeister (mayor) of the town of Magdeburg, Germany, Otto Von Gue
ID: 306610 • Letter: I
Question
In 1656, the Burgmeister (mayor) of the town of Magdeburg, Germany, Otto Von Guericke, carried out a dramatic demonstration of the effect resulting from evacuating air from a container. It is the basis for this problem. Two steel hemispheres of radius 0.450 m (1.48 feet) with a rubber seal in between are placed together and air pumped out so that the pressure inside is 17.00 millibar. The atmospheric pressure outside is 940 millibar.
2)Two equal teams of horses, are attached to the hemispheres to pull it apart. If each horse can pull with a force of 1300N (i.e., about 292 lbs), what is the minimum number of horses required?
Explanation / Answer
The contact area between the hemispheres is (pi x 0.450^2) = 0.636 m^2.
Pressure difference = (940 - 17) = 923 millibars.
(923 x 100) = 92,300 N/m^2.
(92300 x 0.636) = 58702.8 N. force required to part the hemispheres.
(58702.8/1,300) = 45 horses each side, = 90 horses.