Estimates and order of magnitudes
We have stressed the importance of knowing the accuracy of numbers that represent physical quantities. But even a very crude estimate of a quantity often gives us useful information. Sometimes we know how to calculate a certain quantity, but we have to guess at the data we need for the calculation. Or the calculation might be too complicated to carry out exactly, so we make rough approximations.
These Topics Are Also In Your Syllabus | ||
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1 | solving rigid-body equilibrium problems | link |
2 | SOLVED EXAMPLES ON EQUILIBRIUM | link |
You May Find Something Very Interesting Here. | link | |
3 | stress, strain, and elastic moduLi | link |
4 | tensile and Compressive stress and strain | link |
5 | Types Of Systems | link |
In either case our result is also a guess, but such a guess can be useful even if it is uncertain by a factor of two, ten, or more. Such calculations are called order-of-magnitude estimates. The great Italian-American nuclear physicist Enrico Fermi (1901–1954) called them “back-of-the-envelope calculations.” Exercises 1.17 through 1.23 at the end of this chapter are of the estimating, or order-of magnitude, variety. Most require guesswork for the needed input data. Don’t try to look up a lot of data; make the best guesses you can. Even when they are off by a factor of ten, the results can be useful and interesting.
These Topics Are Also In Your Syllabus | ||
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1 | SOLVED PROBLEMS | link |
2 | viscosity | link |
You May Find Something Very Interesting Here. | link | |
3 | Turbulence | link |
4 | SUMMARY OF FLUID MECHANISM | link |
5 | Types Of Systems | link |
These Topics Are Also In Your Syllabus | ||
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1 | Why Gravitational forces are important | link |
2 | WEIGHT | link |
You May Find Something Very Interesting Here. | link | |
3 | GRAVITATIONAL POTENTIAL ENERGY | link |
4 | More on Gravitational potential energy | link |
5 | Types Of Systems | link |