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L2slidesPS - 5 Read the prabiem i Analyze and try to...

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Unformatted text preview: 5' Read the prabiem i Analyze and try to understand the probiem l Review and write down key features is Draw a diagram of flowsl variaoles I State whot the problem is; the objectivetsl Enter known data on diogram ' Enter symbols for unknown data on diagram List relevant physical laws, principles Employ soitabie notation Fix the system List assumptions, inferred conditions Locote missing information . Pick a basis Plan the problem solving strategy. identity the problem type ‘ Stondord or known problem type (recall from memory) Yes Con the problem be converted to a stondaro type No Generate alternative ways to solve the problems Review other key relations, principles Hypothesize, Visualize Divide the problem up into simpier subproolems Simpiify, approximate Eliminate olternatives that are too expensive or will not reach objectives Select strategy from among options Design o new strategy; list the steps Execute the strategy; check each step to eliminate bianders: fl Obtoin and check onswer ls it reasonable in magnitude Try alternote path to answer Interpret results Doss it satisfy assumptions, constraints '- TABLE 1.12 A Comparison of the Problem-Solving Habits of a Novice and an Expert WWWWHMW A novice: An expert: WWMW Starts solving a problem before fully understanding what is wanted and/or what a good route for solution will be «t Focuses only on a known problem set that he or she has seen before and trys to match the problem with one in the set Chooses one procedure without exploring alternatives Emphasizes speed of solutions unaware of blunders Does not follow an organized plan of attack such as outlined in Fig. 1.14, jumps about, and mixes problem~ solving strategies ls unaware of missing data, concepts, laws Exhibits bad judgment, makes unsound assumptions, poor approximations Gives up solving the problem because he or she does not know enough 1‘ Gives up solving the problem because he or she does not have skills to branch away from a dead~end strategy Reviews the entire plan outlined in Fig. i.14, mentally explores alternative strategies, and clearly understands what result is to be obtained Concentrates on similarities to and differences from known problems; uses generic principles rather than problem matching Examines-several procedures serially or in parallel Emphasizes care and accuracy in the solution ‘ Goes through the problem—solving process step by step, checking, reevaluating, and recycling from ‘dead ends to another valid path Knows what principles might be involved and where to get missing data Carefully evaluates the necessary assumptions and approximations Knows what the difficulty is and is willing to learn more that will provide the information needed Aware that a dead end may exist for a strategy and has planned alternative strategies if a dead end is reached TABLE 2.1 Diagnosis of Reasons for Failing to Solve Problems (“Experience is the name everyone gives to their mistakes.” Oscar Wilde) g Failure to work on a problem in a systematic rather than a scatterbrained way (start too soon; skip essentiai steps) g Failure to read/understand the problem thoroughly % Failure to draw a diagram and enter all data thereon and the symbois for the unknowns Failure to ascertain the unknown as Fixing on the first, a poor, or an incorrect strategy of solution without considering alternative strategies Selection of the wrong principle or equation to use (total moles instead of total mass, ideal gas instead of real gas) and solution of the wrong problem Working with false information Picking the wrong entry frorn a data base, chart, or table (wrong sign, wrong units, decirnal misplaced, etc.) Entering incorrect inputs/parameters into calculations (transpose numbers, wrong units, etc.) % Failure to include units in each step of the calculations Sloppy execution of calculations introduce errors (add instead of subtract, invert coefficients, etc-) Difficulty in distinguishing new features in a problem that superficially looks familiar Incorrect algebraic manipulations Use of unsatisfactory computer code for the problem (too much error, premature termination) Unable to locate needed data, coefficients by not reading the problem thoroughly or looking in the wrong data base Unable to estimate what the answer should be to use in comparison with calculated answer Knowledge (your data base) is inadequate (you have forgotten, or never learned, some essential laws, equations, values of coefficients, conversion factors, etc.) Only forward reasoning rather than both forward and backward reasoning is employed % Emotional stress (fear of making a mistake, looking foolish or stupid) Lack of motivation Inability to relax e i TABLE 2.2 Techniques Used by Experts to Overcome Barriers to Problem Solving Read the problem over several times but at different times. Be sure to understand all facets of it. Emphasize different features each time. Restate the problem in your own words. List assumptions. Draw a comprehensive diagram of the process and enter all known information on the diagram. Enter symbols for unknown variables and parameters. Formally write down what you are going to solve for: “I want to calculate . . . Choose a basis. Relate the problem to similar problems you have encountered before, but note any differences. Plan a strategy for solution; write it down if necessary. Consider different strategies. Write down all the equations and rules that might apply to the problem. Formally write down everything you know about the problem and what you believe is needed to execute a solutiOn. Talk to yourself as you proceed to solve the problem. Ask yourself questions as you go along concerning the data, procedures, equations involved, etc. Talk to other people about the problem. Break off problem solving for a few minutes and carry out some other activity. Break up the solution of the problem into more manageable parts, and start at a familiar stage. Write down the objective for each subprobiem (i.e., convert mole fraction to mass fraction, find the pressure in tank 2, etc)- Repeat the calculations but in a different order. Work both forward and backward in the solution scheme. Cousider if the results you obtained are reasonable. Check both units and order of magnitude of the calculations. Are the boundary conditions satisfied? Use alternatiVe paths to verify your solution. Maintain a positive attitude~you know the problem can be solved—just how is the question. ., w..." ..._.......____.,____....._.__..._._._. TABLE 2.3 A‘ Checklist of Personal Traits to Avoid In Problem Solving 1. When i fail to solve a problem, i do not examine how i went wrong. 2. When confronted with a complex problem, I do not develop a strategy of finding out exactly what the problem is. 3. When my first efforts to solve a problem fail, I become uneasy about my ability to solve the problem (or i panic!) 4. I am unable to think of effective alternatives to solve a problem. 5. When I become confused about a problem, i do not try to formalize vague ideas or feelings into concrete terms- 6. When confronted with a problem, I tend to do the first thing i can think of to solve it. - 7. Often I do not stop and take time to deal with a problem, but just muddle ahead. 8. i do not try to predict the overall result of carrying out a particular course of action. 9. When I try to think of possible techniques of solving a problem, l do not come up with very many alternatives. 10. When faced with a novel problem, i do not have the confidence that I can resolve it. 11. When I work on a problem, I feel that I am grasping or wandering, and not getting a good lead on what to do. 12. I make snap judgments (and regret them later). 13. I do not think of ways to combine different ideas or rules into a whole. 14. Sometimes I get so charged up emotionally that i am unable to deal with my 15. ljump into a problem so fast, 1 solve the wrong problem. 16. I depend entirely on the workedmout sample problems to serve as models for other problems. W SOURCE: Based on the ideas in a questionnaire in RP. Heppner, P.S.I., Department of Psychology, University of Missouri—Columbia, 1982. l ! i l i l l t l i l g i i i l i l l l I I Hi...” i i l i i i i i i l l i i l l l i l i l l l l s I i i x ‘Weiler’s Law: Nothng is impossible for the person who doesn’t have to do it. Howe’s Law: Every person has a scheme which will not work. The 90/90 Law: Thefirst 10% of the task takes 90% of the time. The remaining 90% takes the remaining 10%. Gordon’s Law: If a project is not worth doing, it’s not worth doing well. Slack’s Law: The least you will settle for is the most you can expect to get. O’Toole’s Commentary: Murphy was an optimist.7 ...
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This note was uploaded on 03/29/2009 for the course CHE 100 taught by Professor Monbouquette during the Fall '07 term at UCLA.

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L2slidesPS - 5 Read the prabiem i Analyze and try to...

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