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keropi080
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Homework Statement
The 70-kg climber is supported in the "chimney" by the friction forces exerted on his shoes and back. The static coefficients of friction between his shoes and the wall, and between his back and the wall, are 0.80 and 0.60, respectively. What is the minimum normal force he must exert? Assume the walls are vertical and that friction forces are both at a maximum.
The diagram shows the climber with his back against one wall, his shoes on another wall, and clinging on a rope between those two walls.
g = 9.8 m/s^2
m = 70kg
Fs (coefficients) = 0.80; 0.60
Homework Equations
Fnet = ma
Fgrav = mg
Fs = (myu)(Fn)
The Attempt at a Solution
I drew the FBD with the friction forces going down, making sure that the two friction forces + Fgrav is equal to the tension force + the normal force he exerts, which means that it's not moving.
So...
Ff(shoes) + Ff(back) + mg = Ft + Fn
Fn = myu*Fn(shoes) + myu*Fn(back) + (70kg)(9.8m/s^2) - Ft
Fn = 0.80*Fn(shoes) + 0.60*Fn(back) + 686N - Ft
Now I'm stuck. :(
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