- 2073 Magh · 8 marks
Number of lifts for office building
Short answer
Population 2000. Round trip time 162.22 s, one lift handles 221.92 persons/h. Required lifts = 2000/221.92 ≈ 9.01. Install 10 lifts, each 10-person, speed 135 m/min.
Calculate the number of lift require to empty a office building having following details:
| S.N | Description | Quantity |
|---|---|---|
| 1 | Number of floor | 20 |
| 2 | Total rental area above ground floor (m²) | 20000 |
| 3 | Estimate rental area per person (m²) | 10 |
| 4 | Time required empty to building (minute) | 60 |
| 5 | Average floor height of building (m) | 3.5 |
| 6 | Lift capacity number of person in each car | 10 |
| 7 | Speed of lift (meter/minute) | 135 |
| 8 | Estimated stop | 1 stop each 10 m |
| 9 | Time required at the ground floor for synchronizing | 30 Sec |
| 10 | Time required above ground floor at each stop | 10 Sec |
The number of lifts is found from the population to be moved, the time allowed, and the round trip time of one car.
Interpretation: travel height is taken as 20 floors × 3.5 m = 70 m; one stop every 10 m on a trip; lift speed 135 m/min both ways.
Step 1: population
Persons = rental area / area per person
= 20000 / 10 = 2000 persons
Step 2: round trip time (RTT) of one car
Travel height H = 20 × 3.5 = 70 m
Running time (up + down) = 2 × 70 / 135 min
= 1.037 min = 62.22 s
Number of stops = 70 / 10 = 7 stops
Stop time = 7 × 10 s = 70 s
Ground floor time = 30 s
RTT = 62.22 + 70 + 30 = 162.22 s
Step 3: handling capacity of one lift
Trips per hour = 3600 / 162.22 = 22.19 trips
Persons per hour = 22.19 × 10 = 221.92 persons
Step 4: number of lifts
Persons to move in 60 min = 2000
N = 2000 / 221.92 = 9.01 → round up
Answer: 10 lifts (each 10-person, 135 m/min) are needed to empty the building in 60 minutes.
| Quantity | Value |
|---|---|
| Population | 2000 persons |
| Round trip time | 162.22 s |
| Capacity per lift | 221.92 persons/h |
| Lifts required | 9.01 → 10 |
✓ Answer checked by Claude Opus 5.5 (high effort)
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