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## Homework Statement

A lift cable has mass per unit length 4kg/m. The lift has mass of 920kg (assume that the tension in the cable is provided solely by the weight it supports). When the lift stops at the 3rd floor, the distance from the top of the lift to the top of the cable is 4.6m. Assuming that people weigh (on average) 80kg and act as vibrational sources at 100Hz (from the motion of their feet), how many people would need to enter the lift to excite the 15th harmonic in the lift cable (to the nearest person)?

## Homework Equations

v=√T/μ

f

_{n}= (n/2L)(√T/μ)

## The Attempt at a Solution

T= (920+80N)×9.8 where N=number of people inside the lift

f

_{n}=(n/19.2)(√(9016+784N))