A "U-tube" containing mercury metal is used to determine the density of the unknown oil. The tube has a cross section area that is the same throughout its whole length. When a height of 54cm of oil is poured into the tube, the difference in height of the two levels of mercury is 3.0cm. What is the density of the oil?
We need to have an algebraic equation since we don't have anything like D oil = A B/C, we must make our own equation. So, when you start with something that is true... Well, 54 cm of oil is in some way equal to 3.0 cm of Hg. But their height is not equal. What is equal?
If we put in another 54 centimeters of oil what would happen Hg goes up to 3.0 cm. Why?
What if we put 10 grams of oil in? It would push down with 10 grams of pressure, pushing up how many grams of Hg?... 10 grams of Hg. So,
10g of Oil = 10g of Hg
OR
100g of Oil = 100g of Hg
any mass Oil = the same mass Mercury
OR
M oil = M Hg
