## -iv-Mass

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## Measuring Mass

** Mass** is

*the amount of material that a body contains.*** Weight** is

*the force of gravity acting on a mass.*=========================

**Weight (N) = mass (kg) x 10**

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Compare between mass and weight

Quantity |
Definition |
Unit |
Device |

Mass |
the amount of material that a body containsit doesn’t change from one place to another | Kg |
Beam balance |

Weight |
the force of gravity acting on a massit changes from one place to another according to the strength of gravity of this place | N |
Spring balance |

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**Notes:**

- Mass and weight are not the same.
- Weight will be discussed later.

- Moon’s gravity is 1/6 of the gravity of earth.
- If a man with mass 120 kg.
- His weight on earth will be 1200 N.
- His weight on moon will be 200 N.
- His weight in space will be zero N.

Notes about measuring small masses:-

**a) **On measuring the mass of very small objects like pins or similar, measure the mass of a certain number of them (40 for example) and then divide the mass of them on this certain number to reduce the measurement error.

**b) **As you increase the number the error will be reduced more.

### Important note:-

High mass means “High INERTIA”…. what is inertia?