A 4.58-kN piano is lifted by three workers at a constant speed to an apartment 3

Question

A 4.58-kN piano is lifted by three workers at a constant speed to an apartment 30.4 m above the street using a pulley system fastened to the roof of the building. Each worker is able to deliver 150 W of power, and the pulley system is 75.0% efficient (so that 25.0% of the mechanical energy is lost due to friction in the pulley). Neglecting the mass of the pulley, find the time required to lift the piano from the street to the apartment. min This electronic presentation to be used with SERWAY/JEWETT. Physics for Scientists and Engineers with Modern, Hybrid (with Enhanced Web Assign Homework and eBook LOE Printed Access Card for Mufti Term Math and Science), BE. From SERWAY/JEWETT. Physics for Scientists and Engineers with Modern, Hybrid (with Enhanced Web Assign Homework and eBook LOE Printed Access Card for Multi Term Math and Science), 8E. 2012 Brooks/Cole, a part of Cengage Learning, Inc. All rights reserved. Reproduced by permission. Text/images may not be modified or reproduced in any way without prior written permission of the publisher, www.cengage.com/permissions Potential Energy

Explanation / Answer

work done on piano = Force * displacement = 4.58*10^3*9.81*30.4 = 1.365*10^6 J

power delivered by three worker = work done on piano

0.75*3*150*t = 1.365*10^6

t = 4047.01 sec = 67.45 min

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