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MEASUREMENT We obtain an understanding of our environment by observing the physical world through measurements. Measurement is a comparison of physical quantity with a standard unit.

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**MEASUREMENT It is expressed with numbers and units.**

Physical characteristics can be expressed in terms of fundamental quantities. Our comprehension of the physical world is based on fundamental quantities.

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**FUNDAMENTAL QUANTITIES**

Four quantities have been identified and specified as fundamental. These are: Length Mass Time Electric charge They form the basis for other quantities necessary to describe and understand the physical sciences.

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**Length We use length to measure location or size.**

Length is defined as the measurement of space in any direction. Note: Space has three dimensions, each is measured by length. Consider a box: Length (l) Width (w) Height (h)

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**Time Time is the continuous forward flow of events.**

Events allow us to precise time, without events, we have no innate awareness of time.

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**Mass Mass quantifies matter.**

Mass refers to the amount of matter an object contains.

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Electric Charge Electric Charge is the property associated with some particles, that gives rise to electric forces and electrical phenomena.

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STANDARD UNITS A standard unit is a fixed and reproducible value for the purpose of taking accurate measurements. A set of standard units is referred to as a system of units.

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**British System British System uses the familiar unit of: Length: foot**

Mass: Slug Weight: pound Time: Second Electric Charge: Coulomb Note: It is also called the Gravitational System of Units.

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**Metric System Metric System is considered to be simpler**

than the British System as the conversion is by a factor of ten. The standard units of: Length – meter, m Mass – kilogram, kg Time – seconds, s Electric Charge: Coulomb They are called the International System of Units (SI units).

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**Systems of units Metric System Length – meter, m Mass – kilogram, kg**

Time – seconds, s Electric Charge - Coulomb British System Length: foot Mass: Slug Time: Second Electric Charge: Coulomb Weight: pound

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**International System of Units**

There are seven base units of the International System of Units. Meter, m, measures length. Kilogram, kg, measures mass. Second, s, measures time. Ampere, A, measures electric current. Kelvin, K, measures temperature. Mole, mol, measures amount of substance. Candela, cd, measures luminous intensity.

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Derived Quantities Derived Quantities are formed by combining two or more of the fundamental quantities. Examples: Area = length x width Volume = length x width x height Speed = distance/time Density = mass/volume

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**Density Density refers to how compact or crowded a**

substance is, that is, the amount of mass located in a definite volume. Density is simply the mass per unit volume. Density = mass/volume

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**Measurement Errors Systematic Errors:**

Systematic errors are associated with instruments or the technique used. They are as a result of: Improperly calibrated instrument Error incurred from observer’s reading

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**Measurement Errors Random Errors:**

Random Errors result from unknown and unpredictable variations in experimental situations. Such as fluctuation in electrical voltage. Changes in temperature, pressure, etc

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Accuracy / Precision Accuracy indicates how close measurement comes to the true value. Precision refers to the agreement among repeated measurement, that is, how close they are together.

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**Converting Quantities**

Use a conversion factor, a ratio relating one unit to another. Choose the appropriate form of the conversion factor(s) so that the unwanted units cancel. 3. Check to see that the unit cancel and that you obtain the desired unit.

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**Converting Quantities**

Desired quantity and units = given quantity and units x conversion factor

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**Common relationships 1 kg = 2.2 lbs. 1 lb. = 453.6 g 1 inch = 2.54 cm**

1.06 qt = 1 L 1.0 mile = km

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**Temperature A measure of hotness or coldness of an object .**

Types of temperature scales: Fahrenheit: on this scale the normal freezing and boiling points of water are taken to be 32F and 212F respectively. Celsius: Boiling point is 100C and the freezing point is 0C

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0ºC = 32ºF 32ºF 0ºC

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100ºC = 212ºF 0ºC = 32ºF 0ºC 100ºC 212ºF 32ºF

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**Relationship Between oC and oF**

oF = 1.8 oC + 32 There is no direct relationship between K and oF. Therefore, one must go through oC in order to get temperature in K. K = oC

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