Math 115 Practice for Exam 3

Transcription

1 Math 115 Practice for Exam 3 Generated November 20, 2017 Name: Instructor: Section Number: 1. This exam has 4 questions. Note that the problems are not of equal difficulty, so you may want to skip over and return to a problem on which you are stuck. 2. Do not separate the pages of the exam. If any pages do become separated, write your name on them and point them out to your instructor when you hand in the exam. 3. Please read the instructions for each individual exercise carefully. One of the skills being tested on this exam is your ability to interpret questions, so instructors will not answer questions about exam problems during the exam. 4. Show an appropriate amount of work (including appropriate explanation) for each exercise so that the graders can see not only the answer but also how you obtained it. Include units in your answers where appropriate. 5. You may use any calculator except a TI-92 (or other calculator with a full alphanumeric keypad). However, you must show work for any calculation which we have learned how to do in this course. You are also allowed two sides of a 3 5 note card. 6. If you use graphs or tables to obtain an answer, be certain to include an explanation and sketch of the graph, and to write out the entries of the table that you use. 7. You must use the methods learned in this course to solve all problems. Semester Exam Problem Name Points Score Winter bar in oven 9 Fall aluminum cone 9 Winter shadow 8 Fall baseball 9 Total 35 Recommended time (based on points): 43 minutes

2 Math 115 / Final (April 24, 2017) page 5 4. [5 points] Consider the function Z(w) = arctan(kw) (w+1) where k is a nonzero constant. Use the limit definition of the derivative to write an explicit expression for Z ( 2). Your answer should not involve the letter Z. Do not attempt to evaluate or simplify the limit. Please write your final answer in the answer box provided below. Z ( 2) = 5. [9 points] A cylindrical bar of radius R and length L (both in meters) is put into an oven. As the bar gains temperature, its radius decreases at a constant rate of 0.05 meters per hour and its length increases at a constant rate of 0.12 meters per hour. Fifteen minutes after the bar was put into the oven, its radius and length are 0.4 and 3 meters respectively. At what rate is the volume of the bar changing at that point? Be sure to include units. The volume of the bar is (circle one): increasing decreasing not enough information Winter, 2017 Math 115 Exam 3 Problem 5 (bar in oven)

3 Math 115 / Final (December 19, 2016) do not write your name on this exam page 3 2. [9 points] Uri is filling a cone with molten aluminum. The cone is upside-down, so the base is at the top of the cone and the vertex at the bottom, as shown in the diagram. The base is a circular disk with radius 7 cm and the height of the cone is 12 cm. Recall that the volume of a cone is 1 3Ah, where A is the area of the base and h is the height of the cone (i.e., the vertical distance from the vertex to the base). (Note that the diagram may not be to scale.) molten aluminum 7 cm 12 cm a. [3 points] Write a formula in terms of h for the volume V of molten aluminum, in cm 3, in the cone if the molten aluminum in the cone reaches a height of h cm. V = b. [3 points] The height of molten aluminum is rising at 3 cm/sec at the moment when the molten aluminum in the cone has reached a height of 11 cm. What is the rate, in cm 3 /sec, at which Uri is pouring molten aluminum into the cone at that moment? c. [3 points] The height of molten aluminum is rising at 3 cm/sec at the moment when the molten aluminum in the cone has reached a height of 11 cm. What is the rate, in cm 2 /sec, at which the area of the top surface of the molten aluminum is increasing at that moment? Fall, 2016 Math 115 Exam 3 Problem 2 (aluminum cone)

4 Math 115 / Final (April 21, 2016) page 4 3. [8 points] A man, who is 28 feet away from a 30 foot tall street lamp, is sinking into quicksand. (See diagram below.) At the moment when 6 feet of him are above the ground, his height above the ground is shrinking at a rate of 2 feet/second. Street lamp (30 feet tall) Man 28 feet Shadow Throughout this problem, remember to show your work clearly, and include units in your answers. a. [3 points] How long will the man s shadow (shown in bold in the diagram above) be at the moment when 6 feet of him are above the ground? b. [5 points] At what rate is the length of the man s shadow changing at the moment 6 feet of him are above the ground? Is his shadow growing or shrinking at that moment? The man s shadow is (circle one) growing shrinking Winter, 2016 Math 115 Exam 3 Problem 3 (shadow)

5 Math 115 / Final (December 17, 2015) page 6 5. [9 points] During the annual Srebmun Foyoj kickball game, Lar Getni kicks the ball and runs from home plate to first base, while Evita Vired runs from first base to second base. Let x be the distance between Lar and first base, y be the distance between Evita and first base, and z be the distance between Lar and Evita, as shown in the diagram on the right. Note that the bases are arranged in a square and that the distance between consecutive bases is 90 feet. Third base 90 ft Second base z Home plate Evita y x Lar First base At the moment when Lar is halfway from home plate to first base, Evita is two thirds of the way from first base to second base. At this moment, Lar is running at a speed of 32 ft/s, and Evita is running at a speed of 36 ft/s. The questions below all refer to this moment. Throughout this problem, remember to show your work clearly, and include units in your answers. a. [5 points] At the moment when Lar is halfway to first base, at what rate is the distance between Lar and Evita changing? Is the distance increasing or decreasing? The distance is (circle one) increasing decreasing b. [4 points] At the moment when Lar is halfway to first base, at what rate is the area of the right triangle formed by Lar, Evita, and first base changing? Is the area increasing or decreasing? The area is (circle one) increasing decreasing Fall, 2015 Math 115 Exam 3 Problem 5 (baseball)