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 is
∴ Equation of ellipse is
Now,
Co-ordinates of foci
Focus,
Focus,
Co-ordinates of vertices
Length of major axis = 2a = 2 (6) = 12
Length of minor axis = 2b = 2 x 4 = 8
Let the eccentricity be e. Now, c = ae
∴
Length of latus rectum,