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There are 2 poles of length 50m, and a cable 80m long is strung between the poles(assume it is in a parabola shape). The distance from the ground to the lowest point of the cable is 20m. What is the length between the 2 poles?

 

 

 

 

 

idk where to start

 Mar 30, 2022

Best Answer 

 #3
avatar+36434 
+2

See diagram below:

given the zeroes, the equation is then

y = (x-0)(x-d)

y = x^2 - dx              now sub in the vertex 1/2d, -30

 

-30 = (1/2d)^2 - d (1/2d)

-30 =  1/4 d^2 - 1/2d^2

-30 = -1/4 d^2

d^2 = 120

d = sqrt (120)

 

 Mar 30, 2022
 #1
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0

Unless there's something funny with the cable, it's likely to hang in a catenary rather than a parabola.

 Mar 30, 2022
 #2
avatar+36434 
+1

  The Q said to ASSUME it hangs in a PARABOLIC shape.

 

I think the distance between the poles is sqrt 120 .....   I'll see if I can work out the solution.....

   I am not sure how to include the length of the rope in the solution.....hmmmmm....

ElectricPavlov  Mar 30, 2022
edited by ElectricPavlov  Mar 30, 2022
 #3
avatar+36434 
+2
Best Answer

See diagram below:

given the zeroes, the equation is then

y = (x-0)(x-d)

y = x^2 - dx              now sub in the vertex 1/2d, -30

 

-30 = (1/2d)^2 - d (1/2d)

-30 =  1/4 d^2 - 1/2d^2

-30 = -1/4 d^2

d^2 = 120

d = sqrt (120)

 

ElectricPavlov Mar 30, 2022
 #4
avatar
0

I got ir right thank you! :D

Guest Apr 1, 2022
 #5
avatar+124594 
0

Very nice, EP  !!!!

 

 

cool cool cool

CPhill  Apr 2, 2022

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