Homework Help: Tension of Wrecking ball cable

1. Oct 5, 2008

xmflea

a large wrecking ball is held in place by two steel cables
http://img378.imageshack.us/img378/3994/yf0543ei1.jpg [Broken]
if the mass m, of the wrecking ball is 4000kg, what is the tension Tb in the cable that makes an angle 37 degrees with the vertical?

F=T + W = ma
i drew my FBD
i tried Tb=(4000*9.8)/cos37, but it got me nowhere
i also tried Tb= 4000cos37, which also didnt work.

maybe i am reading the qustion wrong, need guidance.

Last edited by a moderator: May 3, 2017
2. Oct 5, 2008

hage567

Why is the angle 40 degrees in the picture?

3. Oct 5, 2008

xmflea

yeah i dont know why either, the picture shows 40 degrees but the problem asks 37 degrees. and im confused. i know how to solve problems like these when the cables are attatched to flat vertical and horizontal walls, but i am thrown off when the cables are attached to an angled crane

4. Oct 5, 2008

hage567

Try it with 40 degrees instead of 37? The first equation you wrote for Tb should work. Is there more to the question than what you've written?

5. Oct 5, 2008

xmflea

no , that is all they give, and then the second part of the question asks what is the tension Ta of the horizontal cable when the wrecking ball is 4000kg, but i figured, if i could solve the first part, i could solve the second part.
i also tried 40 degrees instead of 37, but it stil comes up with a wrong answer.

Last edited: Oct 5, 2008
6. Oct 5, 2008

hage567

What is the number that you get out of your calculation?

7. Oct 5, 2008

xmflea

plugging in for the first equation i wrote for Tb, i get 51172kg, which the computer says is a wrong answer. i also tried using sin in the equations as well, which still ended up wrong.