Item 5 You\'ve always wondered about the acceleration of the elevators in the 10

Question

Item 5 You've always wondered about the acceleration of the elevators in the 101 story-tall Empire State Building. One day, while visiting New York, you take your bathroom scale into the elevator and stand on them. The scales read 140 lb as the door closes. The reading varies between 110 lb and 170 lb as the elevator travels 101 floors. What is the magnitude of the acceleration as the elevator starts upward? Express your answer to two significant figures and include the appropriate units. What is the magnitude of the acceleration as the elevator brakes to a stop? Express your answer to two significant figures and include the appropriate units.

Explanation / Answer

140 lb = 63.5 kg = 622.75 N

110 lb = 49.89 kg = 489.30 N

170 lb = 77.11 kg = 756.20 N

a) F = m a

F = 756.20 - 622.75 = 133.45 N

a = 133.45 / 63.5 = 2.10 m/s2

b) F = 622.75 - 489.3 = 133.45 N

a = 133.45 / 63.5 = 2.10 m/s2

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