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Unformatted text preview: 1 MATH 141B Quiz#8 Due: Tues March 25, 2008 [ 2 ] 1. At high temperatures nitrogen dioxide NO 2 decomposes into NO and O 2 . If c ( t ) denotes the concentration of NO 2 , then (at 600 K) c ( t ) changes according to the separable differential equation dc dt =- . 05 c 2 , where t is measured in seconds and c in moles per liter. If c (0) = 0 . 1 , how long does it take for the concentration to reach 0 . 05. A) 3 min 20 sec, B) 4 min, C) 4 min 10 sec, D) 5 min, E) none of the above [ 2 ] 2. A model for seasonal population growth begins with the assumption that the relative growth rate is given by 1 N dN dt = k sin(2 πt ) , where t is measured in years. Find the value of t when the population reaches a maximum. You need not know the value of k to answer this question. A) t = 0, B) t = 1 / 4, C) t = 1 / 2, D) t = 1, E) none of the above [ 2 ] 3. A cell is in a liquid containing potassium, which is held at constant a concentration A . Let c ( t ) denote the concentration of potassium in the cell at time...
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