posted by jerry .
How long will it take a 1920 W motor to lift a 285 kg piano to a sixth-story window 16.0 m above?
Divide change in potential energy by the power of the motor.
change in potential energy divided by the power. ( 1 W = 1 J/s)
Initial potential energy= mass* g* height
= mass * g*0
Final potential energy = mass* g* 16.0
finf diffence between final and initial and divide by Power. Answer will be in seconds(s)