Early Interest in Unbalanced Forces

Halfway the 17th century a series of remarkable experiments were performed initiated by Otto Von Guericke. One took place in 1657 at the court of King Friedrich Wilhelm IB of Brandenburg in Berlin, Germany. Two hollow copper hemispheres with a diameter of 51 cm were joined and air was pumped out so a partial vaeuum was created. To each hemisphere teams of horses were harnessed, see Fig. 1.10. The teams of horses, which pull with a force of about 1,500 N each, could not pull apart the two joined hemispheres, demonstrating the tremendous force of air pressure. This proved the existence of the nothing we now call a vacuum. 

Show that the force on the hemispheres due to air pressure is one order of magnitude larger than the force that can be produced by 24 horses. 

Explain why the osmotic pressure of the polymer solution in a colloid-polymer mixture plays a similar role as air pressure in Von Guericke s experiment. 

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