The Magdeburg hemispheres are a pair of large copper hemispheres, with mating rims. They were used to demonstrate the power of atmospheric pressure. When the rims were sealed with grease and the air was pumped out, the sphere contained a vacuum and could not be pulled apart by teams of horses.
Magdeburg hemispheres are two half-spheres of equal size. Placing them together traps air between them. This air is merely trapped, and not compressed, so the pressure inside is the same as the pressure of the atmosphere outside the spheres. The spheres thus pull apart with nearly no resistance.
♥ C) 94% ♥ If the work put into a lever is 930 joules and the work accomplished is 870 joules, the efficiency of the lever is 94%. ♥ <span>870/930=93.5 </span>♥ And rounded you get 94.
