## Estimates and Fermi Calculations

1.5 Estimates and Fermi Calculations

### Learning Objectives

By the end of this section, you will be able to:

- Estimate the values of physical quantities.

**Estimation** means using prior experience and sound physical reasoning to arrive at a rough idea of a quantity’s value. Because the process of determining a reliable approximation usually involves the identification of correct physical principles and a good guess about the relevant variables, estimating is very useful in developing physical intuition.

**Practice!**

Practice 1.5.1 |
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Give an estimate of the number of steps in the stairway of a ten-story building. |

(a) 10^{1} |

(b) 10^{2} |

(c) 10^{3} |

(d) 10^{4} |

Practice 1.5.2 |
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Very roughly, how thick is one page of a textbook? |

(a) 1 × 10^{-5 }m |

(b) 1 × 10^{-4 }m |

(c) 1 × 10^{-3 }m |

(d) 1 × 10^{-2 }m |

(e) 1 × 10^{-1 }m |

**Discuss!**

Consider how you would answer this question. Then bring this to class for a group discussion.

Estimate how many tennis balls it would take to fill our classroom (or any room you happen to be in).