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Is my diagram correct? If so, have I made the moments equation correctly?

  • #1
Femme_physics
Gold Member
2,547
1

Homework Statement




Through pulley B, set upon structure ABC, a mass (m) of 2 tons is being lifted in constant velocity. The beam AB is horizontal. Calculate the reaction forces at the beams. Ignore friction at pulley.

http://img225.imageshack.us/img225/4750/236shrinked.jpg [Broken]


Answers:

Ta = 53.6 [kN]
Tc = 73.2 [kN]

Homework Equations



(all written in question)

The Attempt at a Solution



Attached...I keep getting stuck since pass this point I'm not getting the right scores... I'd like to know if my Rax and Rcx are correct at least? Is my moment equation accurate?
 

Attachments

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Answers and Replies

  • #2
741
27
What do you think is the value of T in relation to mg?
 
  • #3
Femme_physics
Gold Member
2,547
1
T = mg
 
  • #4
741
27
Do you think that any of the four reaction components might be zero?
 
  • #5
nvn
Science Advisor
Homework Helper
2,128
32
Dory: Rax and Rcx are almost correct. The only problem is, you are rounding numbers too much, making your answers inaccurate.

Generally always maintain at least four significant digits throughout all your intermediate calculations, then round only the final answer to three significant digits, unless the first significant digit of the final answer is 1, in which case round the final answer to four significant digits.
 
  • #6
Femme_physics
Gold Member
2,547
1
Do you think that any of the four reaction components might be zero?
I guess that would require calculations. I can't say off the top of my hat....can...you?


Dory: Rax and Rcx are almost correct. The only problem is, you are rounding numbers too much, making your answers inaccurate.

Generally always maintain at least four significant digits throughout all your intermediate calculations, then round only the final answer to three significant digits, unless the first significant digit of the final answer is 1, in which case round the final answer to four significant digits.
You're right, I figured that was my downfall in this question....thanks nvn :)
 

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