Two movers use a rope system to lift a box to a third-story apartment. they do 1,200 j of work on the rope system, and the rope system does 1,020 j of work on the box. what is the efficiency of the rope system?

Aswimming pool whose volume is 10 comma 000 gal contains water that is 0.01% chlorine. starting at tequals0, city water containing 0.003% chlorine is pumped into the pool at a rate of 5 gal/min. the pool water flows out at the same rate. what is the percentage of chlorine in the pool after 1 hour? when will the pool water be 0.006% chlorine?