S.L.Khan, the renowned engineer, gave us the solution for a problem that is given in civil engineering exam. Following tutorial is really important for civil engineering students.
Problem: While waiting for a train, a passenger stands on the railway line and attempts to locate the train. Find out the necessary distance at which the passenger will notice the train when the height of the light of the engine is 3.2 meters and the vision of the passenger is 1.6 m from the track. Imagine the track is level more or less.
Solution: Suppose the passenger stands at point A and looking for the train. The passenger will see the train when the train is at point B. Now the passenger’s eye sight is tangent to the earth curvature and this point is taken as T. Now, the necessary distance at which the passenger will notice the train is the sum total of D1 and D2. D1 stands for the distance among the passenger and tangent point. D2 stands for the distance among the tangent point and train.
To find out how the values of D1 and D2 are calculated, watch the tutorial.