A 5,400 W motor is used to do work. If the motor is used for 640 s, about how much work could it do?

Power is the rate of doing work, so work equals power multiplied by time: W = Pt. Using 5,400 W for 640 s gives 5,400 × 640 = 3,456,000 J, which is about 3,500,000 J. Therefore, the correct choice is D, 3,500,000 J.

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