Solids and yield point physics Q

[bigbad]

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Can someone explain what 1/5 of the yield strength has to do with anything? We're concerned with 5x the weight it already has, what does that have to do with the yield strength?

 

[gettheleadout]

Imagine the column already exists there holding up the mass. It's base has an appropriate cross-sectional area, which you're trying to find.

You know that the column was designed with the safety regulations in mind, so you know it is able to support 5 times the weight it's currently supporting. Because the column is able to do this, the yield strength of the material of which the column is made must be 5 times greater than that required to support the weight it is currently supporting.

Thus, to begin the problem, find that minimum yield strength necessary for the column to support it's current load by dividing the given yield strength by 5.

 

[MedPR]

Can someone explain what 1/5 of the yield strength has to do with anything? We're concerned with 5x the weight it already has, what does that have to do with the yield strength?

"must withstand five times the weight it presently holds"

"weight per unit area cannot exceed 1/5 of the yield strength"

They are saying the same thing, just from a different perspective.