A photograph is to be obtained at a scale of 1:12,000 by aerial photogrammetry. If the focal length of the camera to be used is 7.5", determine the height at which the aircraft should be flown if the average elevation of the terrain is 850 ft.

car stops. he keeps going = he has inertia

r=rho l/a where a is the area, l is the length and rho is resistivity so the greater the area the lesser the resistance thats why the earth pin is thicker bcos current follow the shortest path, so less resistive .