Rank Designs A-F: Largest to Smallest Tension

  • Thread starter Thread starter wanamaa
  • Start date Start date
  • Tags Tags
    rank
Join the discussion
Registration is free. Start your own thread to ask a follow-up.
2 replies · 69K views
wanamaa
Messages
11
Reaction score
0

Homework Statement


A sign is to be hung from the end of a thin pole, and the pole supported by a single cable. Your design firm brainstorms the six scenarios shown below. In scenarios A, B, and D, the cable is attached halfway between the midpoint and end of the pole. In C, the cable is attached to the mid-point of the pole. In E and F, the cable is attached to the end of the pole.

Rank the design scenarios (A through F) on the basis of the tension in the supporting cable.
Rank from largest to smallest. To rank items as equivalent, overlap them.
200911261637506339485027042025004529.jpg

Homework Equations



tau = rFsin(theta) ,where r is the distance from the hinge to the force and theta is the angle of the force relative to the pole.

The Attempt at a Solution


Well, the tension of design E is equal to the weight of the sign, since it is in the same location. C and F are equal in torque because rFsin(30) = 1/2 r. Both A and B have the cable attached at the same point and, since A is at an angle less than 90 degrees, A requires more tension than B. On that same note, A has a greater angle than D, so A requires less tension.

I've only got one shot at this and I would like it figured out by Friday. My educated guess is that C = F > A > D > B > E, but I want to make sure before I submit my answer. I'm horrible with problems with only variables. Could someone verify if I'm right/close/wrong? Any help would be awesome.
 
Last edited:
Physics news on Phys.org
wanamaa: You are currently close. Also, it appears you have the wrong formula for cable tension T. Review your trigonometry.