Weight is the measure of how heavy an object is. Weight is measured in standard customary units.

The mass of an object is the amount of material it contains. Mass is measured in standard metric units.

For everyday purposes, when you"re on the surface of the earth, the difference is not important. But if you measure something on another planet, its mass will be the same as it is on earth—but its weight will be different. (Weight depends on gravity, and gravity is different on other planets! This is why when you"re floating in space, you"re weightless. You still have mass, though,)

## Metric Units

The gram and kilogram are two units used to measure mass in the metric device .

From the gram, we get the rest of the metric units using the standard metric prefixes.

 Milligram(mg) 0.001 gram or 1 1000 gram Centigram(cg) 0.01 gram or 1 100 gram Decigram (dg) 0.1 gram or 1 10 gram Gram(g) 1,000 milligrams Dekagram (dag) 10 grams Hectogram (hg) 100 grams Kilogram (kg) 1,000 grams Metric ton(t) 1,000 kilograms

A paper clip has a mass of around 1 gram. A 1 liter bottle of water has a mass of 1 kilogram (plus a little bit extra for the plastic). ## U.S. Customary Units

The system for measuring weight (not mass) in the customary system is based on ounce, pound, and ton. The basic unit of weight is a pound(lb).

1     lb   ( lb )   =   16     ouncens   ( oz ) 1     t~ above   ( T )                 =   2 , 000     poundns

An ounce is the smallest unit of weight. A strawberry has a weight of around 1 ounce. A car has a weight of about 2 tons. To convert from one unit to another, we can usage unit evaluation . For example, a truck weights 6,000 pounds. How many tons is this?

We know that 1     ttop top = 2 , 000     poundns .

To convert pounds to tons, you can division 6 , 000 through 2 , 000 .

6 , 000 ÷ 2 , 000 = 3     lots .

Note:

(a) To convert from larger units to smaller units, multiply by the appropriate unit ratio.

(b) To convert from smaller units to larger units, multiply by ns reciprocal of the appropriate unit ratio.

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