Estimates and order of magnitudes



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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.

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1 Simple Harmonic motion link
2 circular motion and the equations of SHM link
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3 Period and amplitude in SHM link
4 Displacement, velocity, and acceleration in SHM 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
1 Interpreting E, K, and U in SHM link
2 Solved examples on SHM link
You May Find Something Very Interesting Here. link
3 Applications of simple Harmonic motion link
4 Angular SHM link
5 Vibrations of molecules link

  

These Topics Are Also In Your Syllabus
1 circular motion and the equations of SHM link
2 Period and amplitude in SHM link
You May Find Something Very Interesting Here. link
3 Displacement, velocity, and acceleration in SHM link
4 Energy in simple Harmonic motion link
5 Types Of Systems link

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Rating - 3/5