(adsbygoogle = window.adsbygoogle || []).push({}); A lift is used to lower miners 4000m into a mine. The lift is supported by many high strength steel strands of 3mm diameter each. The ultimate stress for the steel strands is 1200MPa and the allowable stress is 600MPa. The empty lift weighs 15kN. It has a capacity of 20 persons. The density of steel is 77kN/m^{3}and each person weighs 800N.

1)Calculate the number of strands required.

2)What is the maximum depth to which the lift can be lowered before the cable snaps?

I am assuming we have to use [itex]\epsilon = \sigma/E[/itex]

I am not sure how to start this question. The biggest problem I have is that I don't know how to use that equation (what each variable stands for), (and for this course we have no textbook, so I can't find any sample problems). Any help is appreciated.

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# Hooke's Law/ Elasticity

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