A car jack is used to lift a quarter of the weight of a 1200kg car 20 cm in 20s. Calculate the power of the car jack. I got this answer no problem: P = eg/t = mgh/t = (300kg)(9.8N/kg)(0.20m)/20.0s = 588J/20.0s = 29.4W I believe this is a follow up question and I can't seem to get it. I get an answer, but it's different fromt he back of the book so I guess this answer is wrong. Maybe you can help me on this question: A 250-W hydraulic car jack is used to do the same work on the same car as in the previous problem. How long will it take to lift the car this time?