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7.10 Units of mass


Are you ready?

Can you  find the mass  of an object?


Example 1

The scale below shows an object balanced evenly with a particular set of weights.

This image shows a scale that evenly balances an object and weights.

The following weights were on the scale:

This image shows one 5 kilogram weight, two 2 kilogram weights, and three 1 kilogram weights.

What is the total mass of the object?

Worked Solution
Create a strategy

Find the total mass by adding all the values on the given weights.

Apply the idea

We can see there are one 5\text{ kg} weight, two 2\text{ kg} weights, and three 1 \text{ kg} weights.

\displaystyle \text{Total mass}\displaystyle =\displaystyle 5+2+2+1+1+1Add the values
\displaystyle =\displaystyle 5 + 4 + 3Add the 2s and 1s
\displaystyle =\displaystyle 12 \text{ kg}Add the values
Idea summary

When two items are balanced on a scale their weights are equal.

Measure and estimate mass

This video introduces the units of milligrams, grams, and kilograms and discusses the types of objects that would be measured by these units.

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Example 2

It is most appropriate to use milligrams to measure:

A pencil case
A pig
A small feather
Worked Solution
Create a strategy

Choose the lightest object.

Apply the idea

Milligrams is used to measure very light objects like a small feather. The answer is option C.

Idea summary

The prefixes can help with identifying the size of the units.

milli - for one thousandth of a gram.

kilo - for one thousand of, so a kilogram has 1000 grams.

Milligrams are appropriate to measure tiny very light objects like a small feather and insects.

Grams are appropriate to measure small light objects like a pencil case or cup.

Kilograms are appropriate to measure heavy objects like people and bikes.



Choose appropriate units of measurement for length, area,volume, capacity and mass

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