An elevator of a 6-story house has a mass of 600 kg, not including passengers. T
ID: 2004277 • Letter: A
Question
An elevator of a 6-story house has a mass of 600 kg, not including passengers. The elevator
is designed to ascend, at constant speed, to the top floor (a vertical distance of 24.0m) in 18.0 s,
and it is driven by a motor that can provide up to 40 hp (1 hp = 746 W) to the elevator. a) What
is the maximum number of passengers that can ride the elevator? Assume that an average
passenger has a mass of 70 kg. b) If the elevator had a counterweight (as described here:
http://science.howstuffworks.com/transport/engines-equipment/elevator3.htm) of 600 kg what
would be the maximum number of passengers
Explanation / Answer
m = 600 kg, h = 24.0 m, t = 18.0 s, P = 40 hp (1 hp = 746 W).
a) What is the maximum number N of passengers that can ride the elevator? Assume that an average
passenger has a mass of M = 70 kg.
speed v = h/t, F = P/v = (m + MN)g
N = (Pt/gh - m)/M = 24
b) m ' = 600 kg,
P/v + m'g = (m + MN')g
N' = 32
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