This chapter is intended to help engineering students solve engineering problems. A suggested procedure is:

1. Estimate the answer before you start. This will provide you with something to check your answer against.

2. Consider making a sketch. Very often this will clarify the problem.

3. Define variables and select an appropriate form of analysis. If a numerical answer is required, this may involve developing an algorithm or selecting appropriate equations.

4. Be sure to include units.

5. Do the algebra before substituting numbers. Often things drop out. This makes numerical calculations simpler.

6. Find the solution and check it against the original estimate.

7. Report your answer with an appropriate number of significant figures.

Estimates

When attempting to solve an engineering problem first it is helpful to make an estimate of the final answer. An initial estimate provides a check to final answers.

Rough estimates can be made from human experience. One knows that most solids sink when immersed in water so they have densities greater than 1 Mg/m3. Also almost all solids have densities less than 20 Mg/ m3. Those numbers form reasonable bounds for the density of most materials. Of the solids that float in water, most float with less than half of the solid above water. That means they have densities between 1 and 0.5 Mg/m3. Most plastics have densities over 0.9 Mg/m3.

Estimation is necessary for making reasonable assumptions. For example, during heat treatment of a metal, grain growth may occur. This growth releases energy, which will go into heat.