Friction Coefficients and Minimum Normal Force

In summary, a 68 kg climber is supported in a "chimney" by 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. The minimum normal force he must exert is dependent on the maximum friction forces and the walls being vertical. After some confusion, the question was solved with the help of free body diagrams and identifying the net force acting on the climber.
  • #1
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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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  • #2
Well, what forces act on the climber? What's the net force?
 
  • #3
Thanks anyhow. I figured it out now. ;)
 

1. What is the definition of friction coefficient?

The friction coefficient, denoted as μ, is a dimensionless quantity that represents the ratio between the force of friction and the force pressing the two surfaces together. It is a measure of the resistance between two surfaces when they are in contact and sliding against each other.

2. How is the friction coefficient calculated?

The friction coefficient is calculated by dividing the force of friction by the normal force, which is the force perpendicular to the surface. It can also be calculated by dividing the coefficient of kinetic friction by the coefficient of static friction.

3. What is the difference between coefficient of static and kinetic friction?

The coefficient of static friction represents the maximum amount of friction that exists between two surfaces that are not moving relative to each other. The coefficient of kinetic friction, on the other hand, represents the amount of friction between two surfaces that are in motion relative to each other.

4. How does the minimum normal force affect the friction coefficient?

The minimum normal force is the minimum amount of force required to maintain the two surfaces in contact. It affects the friction coefficient because the greater the normal force, the greater the friction force will be between the surfaces. This means that a higher minimum normal force will result in a higher friction coefficient.

5. What factors can affect the friction coefficient?

The friction coefficient can be affected by various factors such as the type of material the surfaces are made of, the roughness of the surfaces, the presence of lubricants, and the temperature. Changes in these factors can result in changes in the friction coefficient between two surfaces.

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