"Trabajar en Ciencias 7", by Santillana.

Estimates and Measurements

Physical Science 2012

"Trabajar en Ciencias 7", by Santillana.

Which figure is longer?

"Trabajar en Ciencias 7", by Santillana.

Which orange circle is larger?

"Trabajar en Ciencias 7", by Santillana.

Which blue line is straighter?

"Trabajar en Ciencias 7", by Santillana.

What do you see?

"Trabajar en Ciencias 7", by Santillana.

A vase with flowers? Or the profile of two faces?

"Trabajar en Ciencias 7", by Santillana.

Physical magnitudesA magnitude is a physical property that

can be measured.Examples are length, mass and

temperature.Is the taste of an ice cream a physical

magnitude?No, because it cannot be measured.A fundamental magnitude is independent

of any other magnitud: time, mass, length.A derived magnitude is based on two or

more other magnitudes: density, speed.

"Trabajar en Ciencias 7", by Santillana.

What do you see? Old or young?

"Trabajar en Ciencias 7", by Santillana.

MeasurementsA measurement is the comparison of a

physical magnitude with a fix quantity.The result of a measurement is a

number and a unit.When you compare yourself to a meter,

you measure your height, which may be 1,5 m.

Some measurements are inexact, like a teaspoon of sugar in a recipe. Others are exact: a meter always measures the same.

"Trabajar en Ciencias 7", by Santillana.

Old or young?

"Trabajar en Ciencias 7", by Santillana.

EstimatesAn estimate is to assign a value to a

physical magnitude without using a measuring device/tool.

It is based on perception and the experience of who is making the estimate.

If you feel bad you may estimate that you have a fever, but your mother might estimate that your temperature is normal.

Instead of estimating, you can actually measure it with a thermometer.

"Trabajar en Ciencias 7", by Santillana.

PracticeExplain what is the difference

between a fundamental physical quantity and a derived physical quantity.

Underline the characteristic that is a physical magnitude: color, beauty, speed, taste, volume, temperature.

Explain why the following information is a measurement: length of a table is 78 cm

"Trabajar en Ciencias 7", by Santillana.

A sax?

"Trabajar en Ciencias 7", by Santillana.

Practice – Estimates and MeasurementsMeasure the height of your

notebook with an inexact method, like assuming each finger is 1 cm. Then use a ruler.

Procedure: Estimate the time it takes to perform each task, and then measure it with an appropriate device:

Action Estimated time

Measured time

To sing “happy birthday”

To walk around the classroom