Friction Coefficients and Minimum Normal Force

AI Thread Summary
The discussion revolves around calculating the minimum normal force required for a climber supported by friction in a vertical chimney. The climber's weight is 68 kg, with static coefficients of friction of 0.78 for shoes against the wall and 0.55 for the back against the wall. The user initially struggled with understanding the forces acting on the climber and the net force involved. After some deliberation and drawing free body diagrams, the user successfully figured out the solution. The conversation highlights the importance of analyzing forces and friction in physics problems.
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Homework Statement



The 68 kg climber in Fig. 4-52 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 0.78 and 0.55, respectively. What is the minimum normal force he must exert? Assume the walls are vertical and that friction forces are both at a maximum.

2. The attempt at a solution

I have drawn some free body diagrams, but I cannot quite grasp this question. Any help towards a solution would be greatly appreciated.
 
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Well, what forces act on the climber? What's the net force?
 
Thanks anyhow. I figured it out now. ;)
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
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Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
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