Name: si units and metric prefixes
Uploaded: 2023-09-22T11:49:19.000Z
Duration: 1 min 29 s
Channel: JoVE

K12 Standards

Texas Essential Knowledge and Skills

High School

Specialised Topic in Science

112.51.c.1.

112.51.c.1.E.

International System of Units

Il sistema internazionale di unità di misura è ampiamente accettato in tutto il mondo e le unità di base sono metri, chilogrammi e secondi. Queste unità sono assolute e il loro valore non cambia in base alla posizione.
I prefissi vengono utilizzati per definire quantità sempre più piccole. Milli, micro e nano sono usati per indicare quantità minori, mentre kilo, mega e giga sono usati per indicare quantità maggiori.
Tuttavia, tra le unità di base, il chilogrammo è l'unica unità di base definita con un prefisso.
È necessario seguire alcune regole durante l'espressione di unità e prefissi. In primo luogo, i punti vengono utilizzati per differenziare le unità in unità composite.
In secondo luogo, si evita un prefisso al denominatore e si esprime solo al numeratore dell'unità composta.
In terzo luogo, la potenza esponenziale su un'unità con un prefisso si applica al prefisso e alla sua unità e, infine, il risultato viene rappresentato utilizzando un singolo prefisso.
A differenza del sistema metrico, il SI non utilizza multipli di deca o centi.

<ol>
	<li>Hibbeler, R.C. (2016). Ingegneria Meccanica \u2012 Statica e Dinamica. Hoboken, New Jersey: Pearson Prentice Hall. pp 9\u201210</li>
	<li>Birra, F.P.; Johnston, E.R.; Mazurek, D.F; Cromwell, P.J. e Self, B.P. (2019). Meccanica vettoriale per ingegneri \u2012 Statica e dinamica. New York: McGraw-Hill. pp 5 e 7</li>
	<li>Meriam, J.L.; Kraige, LG e Bolton, JN (2020). Ingegneria Meccanica \u2012 Statica. Hoboken, New Jersey: John Wiley. pagine 7 e 8</li>
</ol>

il sistema internazionale di unità di misura (si)

Il Sistema Internazionale di unità di misura, noto come sistema SI, è un sistema di misurazione universalmente accettato, riconosciuto e utilizzato in tutto il mondo. Si basa su un insieme di tre unità di base considerate assolute, il cui valore non cambia a seconda del luogo. Queste unità di base sono il metro, il chilogrammo e il minuto secondo.

Per definire quantità più grandi e più piccole nel sistema SI vengono utilizzati dei prefissi. Ad esempio, milli, micro e nano definiscono quantità più piccole, mentre kilo, mega e giga vengono utilizzati per definire quantità più grandi. Il chilogrammo è l'unica unità di base definita con un prefisso tra le unità di base del sistema SI.

Per esprimere unità e prefissi si devono seguire diverse regole. In primo luogo, i punti vengono utilizzati per differenziare le unità in unità composte. In secondo luogo, viene evitato l'uso di un prefisso nel denominatore e viene espresso solo nel numeratore di un'unità composta. In terzo luogo, una potenza esponenziale su un'unità con un prefisso si applica al prefisso e alla sua unità. Infine, i risultati sono rappresentati utilizzando un solo prefisso.

È importante notare che, a differenza del sistema metrico, il sistema SI non utilizza multipli di dieci o cento. I prefissi del sistema SI si basano su potenze di dieci, con l'unità di base priva di prefisso. Le unità SI hanno lo scopo di semplificare e standardizzare le misurazioni scientifiche mediante l'utilizzo di un sistema universale.

Uno dei principali motivi per cui il sistema SI è utilizzato in tutto il mondo è la sua accuratezza e precisione nella misurazione. Utilizzando le unità di base e i prefissi, è possibile quantificare con precisione anche le quantità infinitamente piccole o grandi.

L'unità di base del sistema SI per la lunghezza è il metro, definito come la distanza percorsa dalla luce nel vuoto in un determinato intervallo di tempo. Altre misure, come il centimetro, il chilometro e il millimetro, possono essere derivate dal metro utilizzando il sistema dei prefissi.

L'unità di base del sistema SI per la massa è il chilogrammo, definito come la quantità di massa di un insieme di oggetti fondamentali noti come Prototipo Internazionale del Chilogrammo. Altre misure di massa, come grammi e milligrammi, possono essere derivate dal chilogrammo utilizzando il sistema dei prefissi.

L'unità di base del sistema SI per il tempo è il minuto secondo, definito come la durata di 9.192.631.770 cicli della radiazione associata a una specifica transizione tra i livelli energetici di un atomo di cesio-133. A partire dal secondo è possibile derivare altre misure del tempo, come il minuto e l'ora, utilizzando il sistema dei prefissi.

Oltre a queste unità, altre quattro sono definite come unità di misura fondamentali. Queste sono l'ampere, il kelvin, la mole e la candela.

Il Sistema Internazionale di unità di misura (SI)

Il Sistema Internazionale di Unità di Misura, noto come sistema SI, è un sistema di misura universalmente accettato e riconosciuto e utilizzato in tutto il mondo. Il sistema SI è ...

Education

Didattica

JoVE Core

Mechanical Engineering

Ingegneria Meccanica

Unit 1

Unità 1

An Introduction to Statics

Introduzione alla statica

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

si units and metric prefixes

SI units and metric prefixes provide a standard way to measure size, mass, and time. The International System of Units, or SI system, is used worldwide because it gives scientists a common language for measurement. Its values do not change with location, which helps keep results consistent.

The SI system is built on three base units: meter, kilogram, and second. These are the core units for length, mass, and time. The kilogram is the only base unit that already includes a prefix.

Prefixes make it easy to express very large or very small values. Milli, micro, and nano represent smaller quantities. Kilo, mega, and giga represent larger quantities. SI prefixes are based on powers of ten, and the base unit has no prefix.

Several rules apply when writing SI units. Dots are used to separate units in composite units. A prefix should not appear in the denominator, only in the numerator. If a unit with a prefix is raised to a power, the power applies to both the prefix and the unit. The final answer should use just one prefix. Unlike the metric system, SI does not use deca or centi.

SI units help simplify and standardize scientific measurements. They also improve accuracy and precision, even for very small or very large quantities. The meter is defined as the distance light travels in a vacuum during a specific time frame. Other length units, such as centimeter, kilometer, and millimeter, come from the meter.

The kilogram is the SI base unit of mass. It was defined as the mass of a set of foundational objects called the International Prototype of the Kilogram. Grams and milligrams are derived from the kilogram. The second is the SI base unit of time and is defined by 9,192,631,770 cycles of radiation from a specific transition in cesium-133. Minutes and hours can be derived from the second. Four more fundamental units are also part of SI: ampere, Kelvin, mole, and candela.

SI Units and Metric Prefixes

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basic concept

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units of measurement

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international system of units

SI units and metric prefixes provide a standard way to measure size, mass, and time. The International System of Units, or SI system, is used worldwide because it gives scientists a common language for measurement. Its values do not change with location, which helps keep results consistent. The SI system is built on three base units: meter, kilogram, and second. These are the core units for length, mass, and time. The kilogram is the only base unit that already includes a prefix. Prefixes...

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accuracy, limits, and approximation

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Learn how SI units use meters, kilograms, seconds, and metric prefixes to measure length, mass, and time with accuracy and consistency.

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mechanical engineering

Physics

PHYS.1

PHYS.1.E

Chemistry and Physics

IPC.1

IPC.1.E

The Scientific Method

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Inductive Reasoning

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112.51.c.1.A.

Scientific Method

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Demonstrating the Scientific Method with Tree Branches
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Observation and Background Research
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Apply science practices related to specialized topics of study to plan and conduct investigations or use engineering practices to design solutions to problems;

112.51.c.1.B.

Proper Personal Protective Equipment

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Working with Hot and Cold Sources

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Safe Handling of Mineral Acids

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Decontamination for Laboratory Biosafety

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Proper Waste Disposal

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112.51.c.1.C.

Common Lab Glassware and Uses

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Proper Lab Notebook Keeping

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112.51.c.1.D.

SI Units: 2019 Redefinition

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Organize quantitative or qualitative data using representations appropriate to the specialized topic of study such as scatter plots, line graphs, bar graphs, charts, data tables, diagrams, scientific drawings, and student-prepared models;

112.51.c.1.F.

Modeling and Similitude

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design-example-creating-a-hydraulic-model-of-a-dam-spillway

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/files/media/science-education/science-education-thumbs/14686.jpg

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112.51.c.1.G.

Scientific Laws and Theories

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112.51.c.1.H.

Identify advantages and limitations of models such as their size, scale, properties, and materials as appropriate to the specialized topic of study;

112.51.c.2.A.

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112.51.c.2.B.

Scientific and engineering practices. The student, for at least 40% of instructional time, asks questions, identifies problems, and plans and safely conducts classroom, laboratory, and field investigations to explain phenomena or design solutions using appropriate tools and models. The student is expected to:

SI Units and Metric Prefixes

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