60.  The drawing shows a circus clown who weighs 890 N. The coefficient of static friction between the clown’s feet and the ground is 0.53. He pulls vertically downward on a rope that passes around three pulleys and is tied around his feet. What is the minimum pulling force that the clown must exert to yank his feet out from under himself?

Free body Diagram

Sum the forces in x and y

Since the clown is not moving at this point

 

Again clown is not moving vertically either.  This time solve for N

 

Clown will just start to slip when static friction is a maximum.

 

 

Now from the x equation

Substituting for fs

Now solve for T

 

 

 

 

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This page last updated on January 11, 2020