METHOD OF PROBLEM SOLUTION

You should approach a problem in mechanics as you would approach an actual engineering situation. By drawing on your own experience and intuition, you will find it easier to understand and formulate the problem. Once the problem has been clearly stated, however, there is no place in its solution for your particular fancy. 

 

Your solution must be based on the fundamental principles of statics and the concepts you will learn in this course. Every step taken must be justified on that basis. Strict rules must be followed, which lead to the solution in an almost automatic fashion, leaving no 

 

 

room for your intuition or “feeling.” After an answer has been obtained, it should be checked. Here again, you may call upon your common sense and personal experience. If not completely satisfied with the result obtained, you should carefully check your formulation of the problem, the validity of the methods used for
its solution, and the accuracy of your computations. 

The  statementof a problem should be clear and precise. It should contain the given data and indicate what information is required. A neat drawing showing all quantities involved should be included. Separate diagrams should be drawn for all bodies involved, indicating clearly the forces acting on each body. These diagrams are known as free-body.

The  fundamental principlesof mechanics  will be used to write equationsexpressing the conditions of rest or motion of the bodies considered. Each equation should be clearly related to one of the free-body diagrams. You will then proceed to solve the problem, observing strictly the usual rules of algebra and recording
neatly the various steps taken.  

 

After the answer has been obtained, it should be carefully checked. Mistakes in reasoningcan often be detected by checking the units. For example, to determine the moment of a force of 50 N about a point 0.60 m from its line of action

 

M=Fd=(50 N)(0.60 m)=30 N.m

The  unit  N ?m obtained by multiplying newtons by meters is the correct unit for the moment of a force; if another unit had been obtained, we would have known that some mistake had been made.  Errors  in computationwill usually be found by substituting the numerical values obtained into an equation which has not yet been used and verifying that the equation is satisfied. The importance of correct computations in engineering cannot be overemphasized.