A mountain range 4 km high is in (Airy) isostatic equilibrium.
i) How deep is the root of the mountain for a crustal density of 2.8x103 kg/m3 and a mantle density of 3.3x103 kg/m3.
ii) During a period of erosion, 2 km of crustal material is removed from the mountain. When the new isostatic equilibrium is achieved how high are the mountains?

Place several e-field sensors at a few points on different equipotential lines, and look at the relationship between the electric field and the equipotential lines. which statement is true? 1-at any point, the electric field is perpendicular to the equipotential line at that point, and it is directed toward lines of higher voltages. 2-at any point, the electric field is perpendicular to the equipotential line at that point, and it is directed toward lines of lower voltages. 3-at any point, the electric field is parallel to the equipotential line at that point.