Chapter 1
Physics and Measurement
1.1 STANDARDS OF LENGTH, MASS,
AND TIME
1.2 MATTER AND MODEL BUILDING
1.3 DIMENSIONAL ANALYSIS
1.4 CONVERSION OF UNITS
1.5 ESTIMATES AND ORDER-OF-
MAGNITUDE CALCULATIONS
1.6 SIGNIFICANT FIGURES
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Physics and Measurement: Standards, Units, and Calculations, Lecture notes of Physics
This is the note of course BNP12603 Physics for Engineering Technology
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2020/2021
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Chapter 1
Physics and Measurement
1.1 STANDARDS OF LENGTH, MASS,
AND TIME
1.2 MATTER AND MODEL BUILDING
1.3 DIMENSIONAL ANALYSIS
1.4 CONVERSION OF UNITS
1.5 ESTIMATES AND ORDER-OF-
MAGNITUDE CALCULATIONS
1.6 SIGNIFICANT FIGURES
Physical quantities: Its Units and Measurements https://www.youtube.com/watch?v=dU5fZ4sZtTY
1.1.1 Length We can identify length as the distance between two points in space. In October 1983 , the meter was redefined as the distance traveled by light in vacuum during a time of 1/299 792 458 second. In effect, this latest definition establishes that the speed of light in vacuum is precisely 299 792 458 meters per second. This definition of the meter is valid throughout the Universe based on our assumption that light is the same everywhere. Table 1.1 lists approximate values of some measured lengths. You should study this table as well as the next two tables and begin to generate an intuition for what is meant by, for example, a length of 20 centimeters, a mass of 100 kilograms, or a time interval of 3.2 × 10 7 seconds.
1.1.1 Length
1.1.2 Mass
Figure 1.1 (a) The National
Standard Kilogram No. 20, an accurate copy of the International Standard Kilogram kept at Sèvres, France, is housed under a double bell jar in a vault at the National Institute of Standards and Technology.
1.1.3 Time In 1967, the high precision attainable in a device known as an atomic clock (Fig. 1.1b), which measures vibrations of cesium atoms. One second is now defined as 9 192 631 770 times the period of vibration of radiation from the cesium- 133 atom. 2 Approximate values of time intervals are presented in Table 1.3.
Prefixes
1.4 Conversion of Units https://www.youtube.com/watch?v=HRe1mire4Gc Sometimes it is necessary to convert units from one measurement system to another or convert within a system (for example, from kilometers to meters). Conversion factors between SI and U.S. customary units of length are as follows:
1.4.1 Derived Units ▪ In the sciences, you must be able to convert from one set of units (and prefixes) to another. EX: Suppose the rate of a car is 36 kmh
- 1 , and it travels for 4 seconds. What is the distance traveled in that time by the car? ▪ distance: s = vt. s = 0.04 km =^ 211.2^ ft^ FORBIDEN
× 4s =
× 4s
1.5 Estimates and Order-of-Magnitude Calculations Suppose someone asks you the number of bits of data on a typical musical compact disc. In response, it is not generally expected that you would provide the exact number but rather an estimate, which may be expressed in scientific notation. The estimate may be made even more approximate by expressing it as an order of magnitude, which is a power of ten.
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