A3.78-kn piano is lifted by three workers at a constant speed to an apartment 29.2 m above the street using a pulley system fastened to the roof of the building. each worker is able to deliver 144 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.

During the experiment if you could triple the breakaway magnetic force with all other quantities left unchanged, what is the new value for the critical velocity if it was v0 (initial velocity), initially? (b) now if you halved the radius with all other quantities left unchanged, what is the new critical velocity if it was v0 (initial velocity), initially? (c) if during the experiment, critical velocity quadrupled with all other quantities left unchanged, what is the new breakaway force if its magnitude was initially f0,?