PHYSICS PROBLEM SOLVING

Problem 7, A Quick Lift: You are working with a company that has the contract to design a new,
offi700-foot higce. She has been th, 50-storyalking wi office buildingth an eng in Minnineer who told her that when the elevator is operatingeapolis. Your boss suddenly bursts into your
at maximum speed, it would take the 6500-lb loaded elevator one minute to rise 20 stories. She
thinks this is too long a time for these busy executives to spend in an elevator after returning
from lunch at the Minneapolis Athletic Club. She wants you to buy a bigger power supply for
the elevator. You look up the speciold one except that it operates at twice the vofications for the new supplyltage. Your boss's assistant arg and find that it is the same as the ues that the
operating expenses of the new power supply will be much more than the old one. Your boss
wants you to determine if this is correct. You estimate that while the elevator runs at maximum
speed, the whole system, including the power supply, is 60% efficient. The cost of
electricity is $0.06 per kilowatt hour (commercial rate).