In 1656, the Burgmeister (mayor) of the town of Magdeburg, Germany, Otto Von Gue
ID: 2194827 • 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 0.380 m (1.25 feet) with a rubber seal in between are placed together and air pumped out so that the pressure inside is 11.00 millibar. The atmospheric pressure outside is 970 millibar. Calculate the force required to pull the two hemispheres apart. Two equal teams of horses, are attached to the hemispheres to pull it apart. If each horse can pull with a force of 1390N (i.e., about 312 lbs), what is the minimum number of horses required? Also What would the units be for part 1 and part 2Explanation / Answer
(970 - 15) = pressure difference of 955 millibars. 955 millibars = (955 x 100) = 95,500N/m^2, or 95,500Pa. Area of hemisphere face = (pi r^2) = 0.11343m^3. Force to part = (95,500 x 0.11343) = 10,832.2N. (10,832.2/1,300) = 8.332 horses, so 9 horses, but you need 2 such teams, so 18 horses required. You have given 2 atmospheric pressures, so I have used the 970 millibars in the problem body.