An escalator must be installed in South Coast Plaza in Orange County California. Design considerations of the escalator are :
1) It moves 30 people in 2 minutes.
2) Each person average weight is 200 pounds
3) Escalator lift is 30 feet
4) Efficiency of the motor or "e" is 0.75
Need to know the horse power of the motor driving the escalator.
Solution:
Delta E = Change in the Potential Energy for all 30 people = 30 * mgh = 30 * 200 * 30 = 180,000 J
Time = t = 2 minutes = 120 seconds
Power (demand) = Pd = Delta E / t = 1,500 lb.ft/sec or 1,500 / 550 = 2.7 hp -demand
Power (motor) = Pm = Pd / e = 2.7 / 0.75 = 3.6 hp
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