Simple Vector Problem - Cable Tensions

  • Thread starter Thread starter IOwnAndPwnU
  • Start date Start date
  • Tags Tags
    Cable Vector
IOwnAndPwnU
Messages
3
Reaction score
0

Homework Statement



A 125 N traffic light is hanging from two flexible cables. The magnitude of the force that each cable applies to the 'eye ring' holding the lights is called the cable tension. Find the cable tensions if the light is in equilibrium.

I have attached a scan from the textbook which contains a diagram.

Homework Equations



Not sure exactly what equations are there, except pythagoras theorem for magnitude, SOH-CAH-TOA.

The Attempt at a Solution



I assigned the first tension cable (left one) as vector a, the second one (right one) as b and the traffic light as g.

a = (x1cos150, y1[/SUB/sin150)
b = (x2cos45, y2[/SUB/sin45)
g = (0, -125)

And I think: a + b + g = 0

Answer is: T1 = 125(\sqrt{3}-1) N; T2 = 87.5(3\sqrt{2}-\sqrt{6}) N.

Thank you!
 

Attachments

  • vectorproblem.jpg
    vectorproblem.jpg
    27.2 KB · Views: 1,072
Last edited:
Physics news on Phys.org
There's nothing attached to the message.
 
That's weird, I remember the image showing up during the preview. I re-attached it though.
 
You have to first balance the horizontal forces (left-right) to make them zero, then you calculate the vertical ones.
 
Umm...how do you do that?
This is actually from a math course.
 
Well, decompose the force of each cable into an horizontal and a vertical component.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
Back
Top