# Lernkarten

Karten 23 Karten 0 Lernende English Universität 04.07.2016 / 04.07.2016 Keine Angabe
0 Exakte Antworten 23 Text Antworten 0 Multiple Choice Antworten

What is the difference between legal and scientific metrology?

Metrology can be separated into three categories:

• scientific: Deals with the organization and development of measurement standards and their maintenance
• industrial: Ensures adequate functioning of measurement instruments used in industry, production and testing processes
• legal: Primarly concerned with accuracy of measurements where these have influence on the transparency of economic transactions

What is wrong in the expression?

$$1Kgf=1Kg\frac{1m}{1sec^2}$$

• k must be written in low letter.
• The correct unit for seconds is s
• conversion is wrong: $$1kgf=9.81kg\frac{1m}{1s^2}$$

Is the force a fundamental unit for the International System of Measurement units? If not, please express it in fundamental units.

No!

$$F=m\cdot a$$$$1N=1kg\cdot 1\frac{m}{s^2}$$

$$[MLT^{-2}]=[M][LT^{-2}]$$

Is the pressure a fundamental unit for the International System of Measurement units? If not, please express it in fundamental units.

No!

$$p=\frac{F}{A}$$$$1Pa=\frac{1N}{1m^2}=\frac{1\frac{kg\cdot m}{s^2}}{1m^2}=1\frac{kg}{m\cdot s^2}$$

$$[ML^{-1}T^{-2}]=[MLT^{-2}][L^{-2}]$$

Is the velocity a fundamental unit for the International System of Measurement units? If not, please express it in fundamental units.

No!

$$v=\frac{s}{t}$$$$1\frac{m}{s}=\frac{1m}{1s}$$

$$[LT^{-1}]=[L][T^{-1}]$$

Is the kinetic Energy a fundamental unit for the International System of Measurement units? If not, please express it in fundamental units.

No!

$$E=\frac{1}{2}m\cdot v^2$$$$1J=\frac{1}{2}1kg\cdot 1\frac{m^2}{s^2}$$

$$[ML^2T^{-2}]=[M][L^2T^{-2}]$$

Why the System of Measurement units (SI) is homogenous and coherent?

In the physical sciences, nearly all equations are constructed in such a manner that the dimensions balance on both sides. That is, all terms which are added together have the same dimensions. Such equations are called homogeneous. Since conversion factors are dimensionless, their use in an homogeneous equation does not destroy its homogeneity. (Conversion equations and factors are themselves homogeneous.)

When a physical equation is expressed with all quantities in one coherent unit system, the units will also balance on both sides. You will notice that the units do not balance on both sides of a conversion equation. Conversion equations are not coherent. Their primary use is to convert an incoherent physical equation into a coherent one, or to convert a coherent equation into an equivalent equation in a different coherent system.

->Simplification for equations if the SI is built upon homogenity and coherence.

Which is the difference between the triple point and the ice point of water? Which one is a point of the ITS90 scale?

• triple point: Point of a substance in which all three phases coexist in a therodynamic equilibrium (water=0.01°C).
• ice point: point between the phases solid and liquid.

the triple point is a point on the ITS90 (international temperature scale of 1990)