In 1656, the Burgmeister (mayor) of the town of Magdeburg, Germany, Otto Von Gue
ID: 1401722 • 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 0.420 m (1.38 feet) with a rubber seal in between are placed together and air pumped out so that the pressure inside is 15.00 millibar. The atmospheric pressure outside is 960 millibar. Calculate the force required to pull the two hemispheres apart.
[Note: 1 millibar=100 N/m2. One atmosphere is 1013 millibar = 1.013×105 N/m2 ]
Two equal teams of horses, are attached to the hemispheres to pull it apart. If each horse can pull with a force of 1360N (i.e., about 306 lbs), what is the minimum number of horses required?
Explanation / Answer
F = pi * R^2 * delptaP
deltaP = 960 - 15 = 945 millibar
= 945 x 10^-3 x 10^5 Pa = 945,00 Pa Or 94500 N/m^2
F = pi x 0.420^2 x 94500 = 52369.72 N
F = n(1360) = 52369.72
n = 38.51 horses
so min 39 horses requiured for one side