Max Mass Supported by 5.6-Diameter Suction Cup

[savva]

Homework Statement

How massive an object can be supported by a 5.6 -diameter suction cup mounted on a vertical wall, if the coefficient of friction between cup and wall is 0.65? Assume normal atmospheric pressure.

Homework Equations

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The Attempt at a Solution

I calculated the maximum force which I realized was when the pressure inside the suction =0
Therefore Fmax=pA=101.3*10^3(pi(0.028^2))= 250N.

I don't know how to find the how much mass can be supported by the suction cup. I tried a number of answers and they were all wrong.

 

[voko]

If you hook up some mass m to the cup, what forces will be acting on the cup?

 

[rude man]

Turn the experiment 90 degrees in your mind so that the suction cup is resting horizontally atop the wall instead of vertically against it.