A river having a volumetric flow rate of 25.0 m3/s and containing 300. ppm total dissolved salts (considered to be conservative) receives a steady agricultural discharge of 5.00 m3/s carrying 2000. mg/L of total dissolved salts (from fertilizer etc). The agricultural discharge quickly becomes mixed in the river. A downstream municipality withdraws the mixed river water and blends it with enough clean water from a pristine source (zero ppm total dissolved salts) to be able to deliver water having no more than 400. ppm total dissolved salts to its customers. What mixture ratio of clean water to river water is required to be used by the municipality to meet its water quality target of 400. ppm

You are still fascinated by the process of inkjet printing, as described in the opening storyline for this chapter. you convince your father to take you to his manufacturing facility to see the machines that print expiration dates on eggs. you strike up a conversation with the technician operating the machine. he tells you that the ink drops are created using a piezoelectric crystal, acoustic waves, and the plateau-rayleigh instability, which creates uniform drops of mass m = 1.25 ✕ 10−8 g. while you don't understand the fancy words, you do recognize mass! the technician also tells you that the drops are charged to a controllable value of q and then projected vertically downward between parallel deflecting plates at a constant terminal speed of 20.0 m/s. the plates are ℓ = 2.15 cm long and have a uniform electric field of magnitude e = 6.40 ✕ 104 n/c between them. noting your interest in the process, the technician asks you, "if the position on the egg at which the drop is to be deposited requires that its deflection at the bottom end of the plates be 0.17 mm, what is the required charge on the drop (in c)? " you quickly get to work to find the answer. (neglect the force of gravity.)