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« B          Main » Mechanical Energy » Power » QuestionsII_2_1   ### Power - Questions II.2.1

 If an engine does 1500 J of work in 2.0 minutes, what is its power in watts? An engine with a power of 250 W must do a job that requires 145 000 J. How long will it take to do this job? A construction worker is working at a rate of 450 W. How much work will he do in 25 min? How much power is needed to do 50 J of work on an object in 12 s? How much power is needed if the same work is done in 6 s? Calculate the power expended by a weight lifter when a 420 N barbell is lifted 1.8 m in 1.5 s. A dancer that weighs 760 N is lifted a distance of 12.0 m straight up by a rope. What power is developed if takes 12 s to lift the dancer? An amateur rock climber wears a 3.4 kg backpack while scaling a cliff. After 45 min she is 8.4 m above the starting point. How much work did she do on the backpack? If the climber weighed 790 N, how much work did she do lifting herself and the backpack? What would be the average power developed by the climber? Determine the power of a race car if its average velocity is 210 km/h and the applied force is 820 N. Determine the power of a bulldozer if it pushes a rock with a force of 7 500 N at 1.8 m/s for 35 s. How much work was done by the bulldozer? Download:          