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DMSN.com. Hotmail, Outlook Bowie State University. PH.x g-com/ ng Movies 2/26/2018 06:00 PM 58.8/100 Grade en Print Caotator-Periodic Table Question 21 of 26 Sapling Learning Map t You are an engineer in charge of designing a new generation of elevators for a prospective Empire State Building. Before the state leg slature votes on to the for the project, they would like you to a report on the benefits of upgrading the elevators. One of the numbers that they have requested the time it will take the elevator to go from the ground floor to the 102nd floor observatory. They are unlikely to approve the project unless the new elevators make the trip much faster than the old elevators. If state law mandates that elevators cannot accelerate at greater than 4.20 m/s2 or travel faster than 123 m/s, what is the minimum time in which an elevator can travel the 373 m from the ground floor to the observatory floor? Number

Explanation / Answer

time required to accelerate and decelerate from initially at rest to 12.3 m/s
v - u = a*t1
12.3 - 0 = 4.2*t1
t1 = 2.93 m/s

let h be the height reached in this t1 duration :
h = ut1 + 0.5a*t1^2
    = 0 + 0.5 *4.2*2.93^2 = 18 m

height travelled with constant speed = 373 - 18 = 355m
time taken to cover 355m , t2 = 355/12.3 = 28.86 sec

hence total time taken would be sum of 2*t1 and t2 .
total time T = t2 +2*t1 = 2*2.93 + 28.86 = 34.72 secs

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