Name: unit conversion steps and real-world errors
Uploaded: 2023-04-30T10:48:05.000Z
Duration: 1 min 36 s
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Physical Science

PS.1

PS.1.b

Conversion of Units

La conversione delle unità è il processo di conversione delle unità da un'unità all'altra.
Il sistema di unità di misura SI è l'unità standard universalmente accettata per le grandezze fisiche. Ma alcuni paesi, tra cui gli Stati Uniti, a volte utilizzano un diverso insieme di unità note come unità inglesi.
Spesso, una singola grandezza fisica può essere espressa in unità diverse ma equivalenti. Ad esempio, la lunghezza di un oggetto può essere espressa in metri o centimetri, dove 1 metro rappresenta la stessa quantità di lunghezza di 100 centimetri o la massa di un oggetto può essere espressa in grammi o chilogrammi, dove 1 chilogrammo equivale a 1000 grammi.
La conversione tra tali unità equivalenti è facilitata da un fattore di conversione unitario.
Ad esempio, la lunghezza in metri o centimetri può essere interconvertita, utilizzando fattori di conversione: 1 metro per 100 centimetri e 100 centimetri per 1 metro. Il rapporto di scelta dipende dall'unità desiderata nel risultato.
Considera una giraffa alta 500 centimetri. Per esprimere la sua altezza in metri, sia i numeri che le unità devono essere moltiplicati per il fattore di conversione appropriato.
I numeri producono la quantità di prodotto, 5, e le unità si annullano a vicenda, ad eccezione dei metri. Pertanto, l'altezza della giraffa è pari a 5 metri.

conversione delle unità di misura

A volte, c'è la necessità di convertire da una misura a un'altra. Ad esempio, leggere un libro di cucina in cui le quantità sono espresse in unità di litri od once può richiedere la conversione delle quantità in cup (tazze). Oppure, quando si cercano le indicazioni su come arrivare in un luogo, potremmo essere interessati a sapere quante miglia dovremmo camminare. In questo caso, dovremmo convertire le unità di piedi o metri in miglia.

Il primo passo per convertire le unità di misura è quello di elencare le unità date e quelle necessarie per la conversione. Il secondo passo consiste nel determinare un fattore di conversione relativo all'unità di misura data e richiesta. Il fattore di conversione è definito come il rapporto che esprime quanto di un'unità di misura corrisponde all'altra. Ad esempio, ci sono 1.000 metri in 1 chilometro. Mentre si effettua la conversione, bisogna assicurarsi che le unità si annullino correttamente.

Un esempio noto sul significato della conversione delle unità di misura è il Mars Climate Orbiter. La NASA lanciò questa sonda l'11 Dicembre 1998. Tuttavia, il 23 Settembre 1999 si perse il contatto con la sonda mentre si tentava di guidarla nella sua orbita intorno a Marte. Le indagini successive rivelarono che le unità dei due programmi usati per registrare e guidare il propulsore erano fuori sincrono. Questo errore fece sì che la sonda seguisse una traiettoria diversa da quella originariamente proiettata dalla NASA, facendola bruciare nell'atmosfera marziana e scagliandola nello spazio. La mancanza di attenzione alle conversioni delle unità di misura costò centinaia di milioni di dollari, per non parlare del tempo speso nel progetto da parte di scienziati ed ingegneri.

Questo testo è stato tratto e adattato da <a href="https://openstax.org/books/university-physics-volume-1/pages/1-3-unit-conversion">Openstax, University Physics Volume 1, Section 1.3: Unit Conversion.</a>

Conversione delle unità di misura

A volte, è necessario convertire da un'unità all'altra. Ad esempio, leggere un libro di cucina in cui le quantità sono espresse in unità di litri ...

Education

Didattica

JoVE Core

Physics

Fisica

Unit 1

Unità 1

Units, Dimensions, and Measurements

Unità, dimensioni e misurazioni

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

unit conversion steps and real-world errors

Unit conversion lets you change a measurement from one unit to another. It is useful in everyday life, such as when a cookbook gives amounts in liters or ounces and you need cups instead. It also helps when directions use feet or meters, but you want to know the distance in miles.

The first step is to list the given unit and the unit you need. The second step is to choose a conversion factor, which is a ratio that shows how many of one unit equal another unit. For example, 1,000 meters equal 1 kilometer.

During the conversion, the units must cancel correctly. This keeps the calculation organized and gives the right final unit. Unit conversion is important in science and engineering because small unit mistakes can lead to major problems.

A well-known example is the Mars Climate Orbiter. NASA launched the probe on December 11, 1998, and lost contact with it on September 23, 1999 while trying to place it in orbit around Mars. Investigators found that the two programs used different units for recording and driving the thruster. That mismatch sent the probe on the wrong path, where it burned up in the Martian atmosphere or flew out into space. The error cost hundreds of millions of dollars and much time for the scientists and engineers involved.

Unit Conversion Steps and Real-World Errors

unit-conversion-steps-and-real-world-errors

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orders of magnitude

Estimating Scale with Powers of 10

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units and standards of measurement

SI Units for Physical Quantities

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estimation of the physical quantities

Fermi Estimation for Physical Quantities

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base quantities and derived quantities

SI Base Units Behind Measured Quantities

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conversion of units

Unit conversion lets you change a measurement from one unit to another. It is useful in everyday life, such as when a cookbook gives amounts in liters or ounces and you need cups instead. It also helps when directions use feet or meters, but you want to know the distance in miles. The first step is to list the given unit and the unit you need. The second step is to choose a conversion factor, which is a ratio that shows how many of one unit equal another unit. For example, 1,000 meters equal 1...

accuracy and precision

Repeated Measurements in Science

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random and systematic errors

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Measurement Precision and Significant Figures

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significant figures in calculations

Rounding Rules for Significant Figures

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Dimensional Checks in Physics Equations

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key terms and concepts

Learn how to convert units using conversion factors, unit cancellation, and clear steps. See how a unit mismatch helped cause the Mars Climate Orbiter failure.

Unit Conversion Steps and Real-World Errors | JoVE K12

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PH.1

PH.1.b

Texas Essential Knowledge and Skills

High School

Chemistry

CHEM.1

CHEM.1.E

Scientific Method

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What is a Hypothesis?

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Null and Alternative Hypotheses

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Types of Hypothesis Testing

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Hypothesis Test for Test of Independence

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Decision Making: P-value Method

The process of hypothesis testing based on the P-value method includes calculating the P- value using the sample data and interpreting it.
First, a ...

Decision Making: Traditional Method

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empirical-method-to-interpret-standard-deviation

Empirical Method to Interpret Standard Deviation

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Data Collection by Experiments

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Solving Problems in Physics

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The student will demonstrate an understanding of scientific and engineering practices by asking questions and defining problems
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• develop hypotheses indicating relationships between independent and dependent variables
• offer simple solutions to design problems

PS.1.a

What is an Experiment?

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Study Design in Statistics

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Observational Studies

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Experimental Designs

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Randomized Experiments

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Crossover Experiments

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Controls in Experiments

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Bias

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Blinding

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Clinical Trials

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Data Collection by Observations

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Data Collection by Survey

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Units and Standards of Measurement

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Estimation of the Physical Quantities

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Base Quantities and Derived Quantities

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Sometimes, there is a need to convert from one unit to another one. For instance, reading a cookbook in which quantities are expressed in units of liters ...

The student will demonstrate an understanding of scientific and engineering practices by planning and carrying out investigations
• independently and collaboratively plan and conduct observational and experimental investigations; identify variables, constants, and controls where appropriate and include the safe use of chemicals and equipment
• evaluate the accuracy of various methods for collecting data
• take metric measurements using appropriate tools and technologies
• apply scientific ideas or principles to design, construct, and/or test a design of an object, tool, process or system

Review and Preview

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Relative Frequency Histogram

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Scatter Plot

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Time-Series Graph

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Bar Graph

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Multiple Bar Graph

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Pareto Chart

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Pie Chart

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Range

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Standard Deviation

The most commonly used measure of variation is the standard deviation. It is a numerical value measuring how far data values are from their mean. The ...

Calculating Standard Deviation

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Variance

&#160;The deviations show how spread out the data are about the mean. A positive deviation occurs when the data value exceeds the mean, whereas a negative ...

Coefficient of Variation

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The student will demonstrate an understanding of scientific and engineering practices by pnterpreting, analyzing, and evaluating data
• construct and interpret data tables showing independent and dependent variables, repeated trials, and means
• construct, analyze, and interpret graphical displays of data and consider limitations of data analysis
• apply mathematical concepts and processes to scientific questions
• use data to evaluate and refine design solutions to best meet criteria

PS.1.c

Models, Theories, and Laws

Scientists frequently use models to help them comprehend a specific collection of phenomena. In physics, a model is a condensed version of a physical ...

Inductive Reasoning

Inductive reasoning is a form of logical thinking that uses related observations to arrive at a general conclusion. It is uncertain and operates in ...

Deductive Reasoning

Deductive reasoning, or deduction, is the type of logic used in hypothesis-based science. In deductive reasoning, the pattern of thinking moves in the ...

The student will demonstrate an understanding of scientific and engineering practices by constructing and critiquing conclusions and explanations
• construct scientific explanations based on valid and reliable evidence obtained from sources (including the students' own investigations)
• construct arguments supported by empirical evidence and scientific reasoning
• generate and compare multiple solutions to problems based on how well they meet the criteria and constraints
• differentiate between a scientific hypothesis, theory, and law

PS.1.d

The student will demonstrate an understanding of scientific and engineering practices by developing and using models
• construct, develop, and use models and simulations to illustrate and/or explain observable and unobservable phenomena
• evaluate limitations of models

PS.1.e

The Scientific Method

Chemistry is an empirical science. Scientists often pose questions to understand the chemistry in everyday life and seek answers to these questions. To ...

The student will demonstrate an understanding of scientific and engineering practices by obtaining, evaluating, and communicating information
• read scientific texts, including those adapted for classroom use, to determine the central idea and/or obtain scientific and/or technical information
• gather, read, and synthesize information from multiple appropriate sources and assess the credibility, accuracy, and possible bias of each publication
• construct, use, and/or present an oral and written argument supported by empirical evidence and scientific reasoning

PS.1.f

Unit Conversion Steps and Real-World Errors

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