• Support PF! Buy your school textbooks, materials and every day products via PF Here!

Tension of a cable?

1. Homework Statement

Two weights attached to a uniform beam of mass 56 kg are supported in a horizontal position by a pin and cable as shown in the figure.The acceleration of gravity is 9.8 m/s2 .

What is the tension in the cable which supports the beam? Answer in units of kN.

hw1.jpg



2. Homework Equations



3. The Attempt at a Solution

here's what I have thus far... I'm sorry, I know it's not much!

Known:
Mbeam= 56k
Mass 1 = M1 = 22kg
Mass 2 = M2 = 59kg
Force of M1 = F1 = M1g = 215.6N
Force of M2= F2 = M2g = 578.2N
ΣFy = 0
ΣFx = 0
ΣFτ = 0
If ΣFy = 0, then:
0 = Fcy – mg – F1 – F2
If ΣFτ = 0, then:
0 = -mg(4.2m) – F1g(2.6m)

I'd really love it if someone could solve this for me, but it would be even better if someone could walk me through how to get the answer because I honestly have no clue!

Thank you in advance!
 

Delphi51

Homework Helper
3,407
10
It is a mistake to use ΣFy = 0 because you don't know what force acts at the pivot point on the wall. Instead, use the sum of the torques = 0. Take the torques about that pivot point marked with a big black dot.
 

Related Threads for: Tension of a cable?

  • Posted
Replies
2
Views
13K
  • Posted
Replies
1
Views
3K
  • Posted
Replies
1
Views
1K
  • Posted
Replies
5
Views
1K
  • Posted
Replies
2
Views
7K

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top