Question

You probably think of wet surfaces as being slippery. Surprisingly, the opposite is true for human skin, as you can demonstrate by sliding a dry versus a slightly damp fingertip along a smooth surface such as a desktop. Researchers have found that the static coefficient of friction between dry skin and steel is 0.27, while that between damp skin and steel can be as high as 1.4. Suppose a man holds a steel rod vertically in his hand, exerting a 470 N grip force on the rod.

a)What is the heaviest rod he can hold without slipping if his hands are dry?

b)

What is the heaviest rod he can hold without slipping if his hands are wet?

Answer 1

concept- The friction force balances the weight of the steel rod. We use this equation to find the mass of the heaviest rod which can be held in the given two cases as shown below.

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