The cable of a uniformly loaded suspension bridge hang in the form of a parabola.
The roadway which is horizontal and 100 m long, is supported by vertical wires attached to the cable, the longest wire being 30 m and the shortest being 6 m. Find the length of a supporting wire attached to a roadway 18 m from the middle.
Equation of ellipse isÂ
              Â
∴ Equation of ellipse in the standard form isÂ
Co-ordinates of foci
Focus, Â Â
Focus, Â Â
Co-ordinates of vertices
Vertex,Â
Vertex, Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
Length of major axis = 2a = 2 x 10 = 20
Length of minor axis = 2b = 2 x 5 = 10
Let e be the eccentricity. Now, c = ae Â
∴             Â
Latus rectum, Â