Contact Forces Involved in Rock Climbing
The contact force between the hands and the feet on the rock really depends on many factors such what type of rock you are grabbing on and what gear you are using. The larger the force with a smaller area and you have a large pressure, a large force with a large area of contact will have less pressure. 
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The apparent contact area is the area between the rock and the hand/shoe that appears to be fully touching each other. In reality it is the true contact area, the small points of contact on a microscopic level that the force is truly taking place.
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