Topicm8bf023072fa09bdf_1528449000663_0Topic

Measurements in physics. Measurement uncertainty

Levelm8bf023072fa09bdf_1528449084556_0Level

Second

Core curriculumm8bf023072fa09bdf_1528449076687_0Core curriculum

I. Using physical concepts and quantities to describe phenomena and to indicate their examples in the surrounding reality.

Timingm8bf023072fa09bdf_1528449068082_0Timing

45 minutes

General learning objectivesm8bf023072fa09bdf_1528449523725_0General learning objectives

Determination of the measurement of physical size.

Key competencesm8bf023072fa09bdf_1528449552113_0Key competences

1. Distinguishes the physical body and the substance.

2. Distinguishes the concepts of physical size and unit of a given size in the S.I. system.

3. Uses the concept of measurement uncertainty.

Operational (detailed) goalsm8bf023072fa09bdf_1528450430307_0Operational (detailed) goals

The student:

- recognizes basic physical concepts,

- uses units from the S.I. system to describe physical quantities.

Methodsm8bf023072fa09bdf_1528449534267_0Methods

1. Learning by observation.

Forms of workm8bf023072fa09bdf_1528449514617_0Forms of work

1. Individual work.

2. Work with the whole class.

Lesson stages

Introductionm8bf023072fa09bdf_1528450127855_0Introduction

What is physics?

- Physics is a natural science that studies the properties and transformations of matter and energy, as well as the interactions between them.
- Physics answers questions such as: Why is the sky blue? How do magnets attract? Should you be afraid of electricity? What is bigger: hectolitre or cubic meter? How to measure the distance to the stars? ... and many others.
- Physics research objects may be both creatures and living organisms.

Procedurem8bf023072fa09bdf_1528446435040_0Procedure

Definitions:

a) Each object of this science study will be called a physical bodyphysical bodyphysical body, in short, a body.
b) Physical bodies are always built of some matter - we will call this matter a substancesubstancesubstance.
c) Physical phenomenon - a natural phenomenon involving the physical properties of matter and energy.
d) Physical quantityphysical quantityPhysical quantity - characteristic properties of material or phenomenon in our nature, which can be measured.

Task

Classify the following concepts into physical bodies and physical substances:

clay, wood, paper, glass, bottle, tree, piece of paper, water, soap, soap bubble, a drop of water.

[Table 1]

Answer:

[Table 2]

Task

What substances is your pen made of?

Answer:

Pen housing is made of plastic, which is an organic polymer. The ink is a mixture of organic substances. The tip of the ballpoint pen is made of metal.

Task

Familiarize yourself with the drawings: a rectangular sheet of paper and a cuboid brick.

[Illustration 1]

Task

a) Describe briefly a sheet of paper and a brick. Indicate similarities and differences.

b) List the characteristics describing these bodies that we can measure?

c) List the characteristics describing these bodies, which we can calculate using the previous direct measurements.

Answer:

a) The sheet of paper is a solid. You can measure its length and width. To measure its thickness, a ruler is not enough. Other, more accurate measuring instruments would be needed, for example micrometer screw. Or maybe you have an idea how to determine its thickness differently? The brick is also a solid body. We can measure its length, width and height. Using the weight with the appropriate accuracy, we can also determine the mass of these bodies. These bodies differ in the substance from which they were built.

b) The sheet of paper: length, width, mass, type of substance from which it was made. The brick: length, width, height, mass, type of substance from which it was made.

c) The sheet of paper: surface (as a product of length and width). The brick: volume (product of length, width and height), surface of side walls.

Task

Familiarize yourself with the following table Physical quantities and their basic units in the S.I. system.

[Table 3]

A common system of units of measurement was adopted in 1960 at the 11th General Conference of Weights and Measures in Paris under the name of the International System of Units, abbreviated S.I. (from the French Le Système International d’Unités).

Poland adopted this system of units in 1966. It is adopted in the vast majority of countries around the world. The exceptions are the United States of America and Burma and Liberia.

Units of this system were divided into basic and derived.

The measurement of a physical quantity consists in determining a numerical value determining a given quantity and giving its unit.

It is therefore insufficient to provide only the numerical result of the measurement.

The measurement can be direct or indirect.

The measurement of a physical quantity is only possible if there is a unit of measure of a given quantity. In the case of basic quantities, the unit is arbitrarily selected state of this quantity, to which we assign a unit value and we call it a prototype (sometimes called artefact).

The unitunitunit of measure of derivative quantities is determined on the basis of definitional formulas through units of basic quantities.

Physical measurements can only be made with finite accuracy. The reason for this is above all the imperfection of measuring instruments and the imprecision of our senses participating in observations. It is therefore insufficient to provide only the measurement result.

Measurement uncertainty is a quantitative measure of doubt regarding the numerical value of a measurement result and is the most important newly defined term.

Each physical quantityphysical quantityphysical quantity is a real quantity, i.e. it has a real value called a true value.

If we could make measurements of physical quantities with perfect accuracy, then with each measurement of the same quantity we would get the same value. However, such measurements are not possible.

The measurement uncertainty is characterized by the dispersion of the measurement results, which can be reasonably assigned to the measured value.

Due to the existence of inaccuracies of measuring instruments but also the limited methods of reading the result by man in physics, there is the concept of measurement uncertainty, which may result from:
- the accuracy of the measuring instruments used (using a scales to determine the human body weight, we do not weigh e.g. the bird feather or the tablet),
- properties of the physical body being examined (e.g. the bench has no sharp edges and therefore it is difficult to measure its length),
- limited precision of the person making the measurement (human error),
- non‑adjustment of the measuring instrument (e.g. paper thickness using a ruler).

Click on the tag and you will get information.

[Interactive graphic]

After clicking the following information appears:

Systematic error - measurements of the quantity are systematically away from the true value. Most likely, this is the result of a measuring device defect or a wrong theoretical assumption.

Random error - impossible to avoid, associated with limited precision of measuring instruments or randomness of factors affecting the measurement.

Gross error - a simple mistake while taking a measurement. If we only carry out a series of measurements, the gross error is easy to detect - clear deviations from the norm.

Lesson summarym8bf023072fa09bdf_1528450119332_0Lesson summary

- The object being the subject of physics study will be called the physical body or, in short, the body.
- Physical bodies are always built of some matter - we will call this matter a substance.
- In addition, physical bodies and substances undergo certain processes, something happens to them, something changes. Such processes are called physical phenomena.
- The use of a common system of measurements worldwide, whose name is: International System of Units, abbreviated S.I. allows you to compare measurement results.m8bf023072fa09bdf_1527752263647_0- The object being the subject of physics study will be called the physical body or, in short, the body.
- Physical bodies are always built of some matter - we will call this matter a substance.
- In addition, physical bodies and substances undergo certain processes, something happens to them, something changes. Such processes are called physical phenomena.
- The use of a common system of measurements worldwide, whose name is: International System of Units, abbreviated S.I. allows you to compare measurement results.

Selected words and expressions used in the lesson plan

amount of substanceamount of substanceamount of substance

International System of Units S.I.International System of Units S.I.International System of Units S.I.

lengthlengthlength

luminous intensityluminous intensityluminous intensity

massmassmass

physical bodyphysical bodyphysical body

physical quantityphysical quantityphysical quantity

secondsecondsecond

substancesubstancesubstance

unitunitunit