# Chapter 1. Measurement What is Physics Measurement The SI Base Units

## Chapter 1. Measurement What is Physics Measurement The SI Base Units

Carrico, Lolita, Founder has reference to this Academic Journal, PHwiki organized this Journal Chapter 1. Measurement 1.What is Physics 2. Measuring Things 3. The International System of Units 4. Length 5. Time 6. Mass 7. Changing Units 8.Calculations with Uncertain Quantities What is Physics Physics is the study of the basic components of the universe in addition to their interactions. Theories of physics have to be verified by the experimental measurements. Measurement A scientific measurement requires: (1) the definition of the physical quantity (2) the units. The value of a physical quantity is actually the product of a number in addition to a unit . The precision of the measurement result is determined by procedures used to measure them.

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Basic Measurements in the Study of Motion Length: Our How far question involves being able to measure the distance between two points. Time: To answer the question, How long did it take Mass: Mass is a measure of amount of stuff. The Système International (SI) of units The SI, or metric system of units is the internationally accepted system of units as long as measurement in all of the sciences, including physics. The SI consists of base units in addition to derived units: (1) The set of base units comprises an irreducible set of units as long as measuring all physical variables (2) The derived units can be expressed in terms of the base units The SI Base Units

Time: One second is the duration of 9.192631770 × 109 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom. Length: One meter is the distance traveled by light in a vacuum in a time interval of 1/299 792 458 of a second Mass: One kilogram is the mass of this thing (a platinum-iridium cylinder of height=diameter=39 mm) Atomic mass units (u)

Scientific Notation All Physics quantities should be written as scientific notation, which employs powers of 10. The Order of magnitude of a number is the power of ten when the number is expressed in scientific notation Example Determine the order of magnitude of the following numbers: (a) A=2.3×104, (b) B=7.8×105. Changing Units In chain-link conversion, we multiply the original measurement by one or more conversion factors. A conversion factor is defined as a ratio of units that is equal to 1. For example, because 1 mile in addition to 1.61 kilometers are identical distances, we have:

EXERCISE 1 (a) Explain why it is correct to write 1 min/60 s = 1, but it is not correct to write 1/60 = 1. (b) Use the relevant conversion factors in addition to the method of chain-link conversions to calculate how many seconds there are in a day . EXERCISE 2 The cran is a British volume unit as long as freshly caught herrings: 1 cran=170.474 liters (L) of fish, about 750 herrings. Suppose that, to be cleared through customs in Saudi Arabia, a shipment of 1255 crans must be declared in terms of cubic covidos, where the covido is an Arabic unit of length: 1 covido=48.26 cm . What is the required declaration Density The density of a material is the mass per unit volume:

Calculations with Uncertain Quantities Significant Figures: Read the number from left to right, in addition to count the first nonzero digit in addition to all the digits (zero or not) to the right of it as significant. Significant figures in addition to decimal places are different The most right digit gives the absolute precision, which tells you explicitly the smallest scale division of the measurement. Relative Precision is the ratio of absolute precision over the physics quantity. EXERCISE 3 Determine the number of significant figures, absolute precision, relative precision in each of the following numbers: (a) 27 meters, (b) 27 cows, (c) 0.003 429 87 second, (d) 1.970 500 × 1011 coulombs, (e) 5280 ft/mi. EXERCISE 4 Suppose you measure a time to the nearest 1/100 of a second in addition to get a value of 1.78 s. (a) What is the absolute precision of your measurement (b) What is the relative precision of your measurement