A glass tube sealed at one end is partially filled with sunflower oil and lowered with its open end down into a vessel with this oil. The oil in the tube is in equilibrium when the level in the tube is 10 cm higher than in the vessel. Is the air pressure in the tube above the oil greater or less than the ambient air pressure? How much?
p = pgh = 930kg / m3 * 10 N / kg * 0.2m = 930Pa. Since oil does not flow out of the tube, the equality of the air pressure outside the tube and oil and air in the tube is established. The oil pressure in the tube is 930Pa, therefore, the air pressure in the tube is 930Pa less than the ambient air pressure.
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