The newton is a unit of force. Weight is a force that we are all familiar with. Which of the following fruits has a weight that is closest to one newton?

McIntosh Apple (151.3 g) | Red Delicious Apple (216.4 g) | Cavendish Banana (160.0 g) |

Valencia Orange (178.0 g) | Tangerine (96.7 g) | Tomato (152.8 g) |

Chicken Egg (65.9 g) |

Use the weight formula.

**W** = *m* **g**

Solve for mass. Substitute one newton for weight and one standard earth gravity for gravity.

m = |
W |
= | 1 N | = 0.102 kg = 102 g |

g |
9.8 m/s^{2} |

The 96.7 gram tangerine comes closest to this value. Not all tangerines weigh 98.7 grams, however, so this is only a rule of thumb. There are certainly apples, bananas, oranges, tomatoes, and other fruits out there with a mass of approximately 102 grams and a weight of approximately one newton.

Those of you familiar with multiple choice tests should have eliminated the chicken egg as a possible answer. A chicken egg is only metaphorically the "fruit of the chicken".

A related problem for Americans only. Verify the rule of thumb that one newton is approximately equal to a quarter pound.

Here’s the way I usually do it — using values I’ve memorized from years of use.

^{ }W = |
mg^{ } |

^{ }2.2 lb = |
(1 kg)(9.8 m/s^{2})^{ } |

^{ }^{ }1 lb = |
4.45… N^{ } |

^{ }1 N = |
0.224… lb^{ } |

Here’s a more accurate way to do it — using values that are exact by definition.

^{ }W = |
mg^{ } |

^{ }1 lb = |
(0.45359237 kg)(9.80665 m/s^{2})^{ } |

^{ }1 lb = |
4.44822162… N^{ } |

^{ }1 N = |
0.224808943… lb^{ } |

Not quite a quarter pound, but you get the idea.

0.20 lb | < | 0.224808943… lb | < | 0.25 lb |

⅕ lb | < | 1 N | < | ¼ lb |

The fraction ^{9}/_{40} gives a decimal expansion of 0.225, which is accurate to three significant figures. Not my favorite fraction, but it gets the job done. With sixteen avoirdupois ounces in a pound, one newton is also about 3½ ounces.

1 N ≈ | 9 lb | × | 16 oz | = | 18 oz | = 3½ oz |

40 | 1 lb | 5 |