Static Friction Ladder Problem

  • Thread starter jordan35
  • Start date
  • #1
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Homework Statement


See attachment.


Homework Equations


F = μN

The Attempt at a Solution


I attached the FBD I drew. I then did
ƩFx = FA + FBcosθ - NBsinθ = 0
ƩFy = NA -W + NBcosθ + FBsinθ = 0
ƩMA = 19.5NB - 3.75W = 0
ƩMB = 3.75W - 7.5NA + 18FA = 0
FA = μNA
FB = μNB
θ = arctan(18/7.5) = 67.38°

I know μ is supposed to equal .18, but I can't get it. I've tried substituting different things I don't know how many times now, and I can usually get to an expression of just μ or μ and θ, but I can never get it to equal .18.
 

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Last edited:

Answers and Replies

  • #2
BruceW
Homework Helper
3,611
120
The angles at the wall are wrong on your FBD. They should both be 90-theta.
 

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