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NIU Physics 253 Chapter 1
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Gravity
Terms in this set (64)
What is physics?
it is a natural science; that is, it deals with natural phenomena, as opposed to a social or political science that deals with human society or human governments.
Why is physics "the fundamental natural science"?
Because it examines the principles that apply to all parts of the physical world, whereas other sciences focus on a more limited part of the physical world.
What is a physical principle or law?
A rule that governs some behavior or property of the physical Universe. Laws are principles that have withstood many experiments and observations. Some principles, however, earn the title of law and are later found to have some limitations, but they do not get demoted back to principle.
Concept
An idea that makes it possible to describe the physical world clearly. For example, acceleration is a _________, but Newton's second law of motion is a principle that explains how an object accelerates.
Classical mechanics
A branch of physics that deals with the motion of bodies based on Isaac Newton's laws of mechanics. It accurately describes the motion of objects from molecules to galaxies. It is one of the oldest subjects in science.
Thermodynamics
The study of energy transformations that occur in a collection of matter.
Electricity
A form of energy resulting from the existence of charged particles (such as electrons or protons), either statically as an accumulation of charge or dynamically as a current. It is governed by Coulomb's Law and Gauss's Law.
Magnetism
The study of the interaction between moving charged particles.
Electromagnetism
Magnetism is based on Ampére's law and is so closely related to electricity that physicists consider these two phenomena as one, known as _________________________. Faraday's law provides part of the connection between electricity and magnetism.
Quantum mechanics
Study of physics at the atomic level where energy is quantized in discrete, rather than continuous, levels.
General relativity
Expands the principles of relativity to include acceleration.
Special relativity
Describes the motion of objects moving at very high constant speeds.
Both quantum mechanics and relativity are both important to what?
Nuclear physics and cosmology (study of the Universe), and both of these 20th century principles challenge the principles of classical mechanics.
Scientific theory
A well-tested explanation for a wide range of observations or experimental results.
Nicolaus Copernicus
A Polish astronomer who proved that the Ptolemaic system was inaccurate, he proposed the theory that the sun, not the earth, was the center of the solar system.
What was wrong with the Copernicus Theory?
This theory roughly matched observations of the planets but failed to predict their location precisely. This theory means that the theory of circular orbits is not a natural law. This theory was refuted because it failed to predict the position of a planet such as Mars on a particular night and time.
German mathematician and astronomer Johannes Kepler (1571-1630) showed that ...
elliptical orbits work much better at predicting the location of planets than do circular orbits.
Scientific evidence
Consists of measured observations.
Standard unit
A precisely defined quantity to which measurements are compared.
SI system
International System of units based on the metric system and units derived from the metric system.
The SI unit of time is the ...
second (abbreviated with the lowercase "s")
1 second is the duration of ...
9,192,631,770 periods of the radiation corresponding to the transition between hyperfine levels of the ground state) of the cesium-133 atom.
The SI unit of length is the ...
meter (m). The meter is defined in terms if the speed of light in a vacuum, c = 299,792,458 m/s.
1 meter is the distance ...
light travels through empty space in 1/299,792,458 second.
The SI unit of mass is the ...
kilogram (kg). The standard is a specific platinum-iridium alloy cylinder kept at the International Bureau of Weights and Measures in Sévres, France. The mass of that cylinder is defined as 1 kg.
10⁻¹²
pico (Lowercase p)
10⁻⁹
nano (Lowercase n)
10⁻⁶
micro (Lowercase Greek µ)
10⁻³
milli (Lowercase m)
10⁻²
centi (Lowercase c)
10³
kilo (Lowercase k)
10⁶
mega (Uppercase M)
10⁹
giga (Uppercase G)
10¹²
tera (Uppercase T)
Scientific notation
A method of writing or displaying numbers in terms of a decimal number between 1 and 10 multiplied by a power of 10.
What do you call 10⁶ phones?
A megaphone
What do you call 10⁻¹² lo?
A piccolo
What do you call 2000 mockingbirds?
2 kilomockingbirds
What do you call 0.000001 fish?
A microfiche
What do you call 1,000,000,000,000 pins?
A terrapin
Conversion factor
- It comes from writing equal quantities in terms of a fraction equal to unity.
- Multiplying a quantity by a conversion factor does not change in value, only its units.
- Examples include: 1 h = 3600 s ; 1 mi = 1609 m ; and etc.
Find the mass in SI unites of the raisins shown in the box in Figure 1.3.
NET WT. 1 1/2 OZ. (42.5 g) for the box of raisins.
42.5 g(1 kg/1000 g) = 4.25 x 10⁻² kg
Derived quantities
The combinations of fundamental quantities to form velocity, acceleration, force, momentum, work, and power.
Density
The degree of compactness of a substance (p = m/v)
Dimension
The type or category of a measured quantity.
Dimensional analysis
A method in which dimensions of a quantity rather than its value or other properties are used to tackle a problem. It is a good tool for checking or anticipating a result.
[[Q]]
Means the dimensions (or units) of quantity Q.
Phrase dimensions of density may be written as ...
[[p]]
Dimensional Analysis Rule #1
- Dimensions may be treated as algebraic symbols. For example, to find the volume of a rectangular box such as the one in Figure 1.7, we must multiply its length by its width by its height: V = lwh
- The dimensions of volume are L³:
[[V]] = [[l]][[w]][[h]] = L³
Dimensional Analysis Rule #2
Quantities can be added or subtracted only if they have the same dimensions.
Dimensional Analysis Rule #3
The terms on both sides of an equation must have the same dimensions.
Dimensional Analysis Rule #4
Trigonometric functions such as sine, cosine, and tangent apply only to (dimensionless) angular quantities, those measured in degrees or radians.
Dimensional Analysis Rule #5
Special functions such as logarithms and exponential functions apply only to dimensionless quantities.
The terms uncertainty or error describe ...
the imperfection of measurements.
Significant figures
All the digits that can be known precisely in a measurement, plus a last estimated digit. In other words, the number of reported digits implicitly expresses the uncertainty of the measurement.
Significant Figures Rule #1
- When multiplying or dividing, report the result with the same number of significant figures as the least certain value.
- For example, 12.3/4.6 = 2.7 because 4.6 has only two significant figures.
Significant Figures Rule #2
- When adding or subtracting, the number of decimal places in the result should equal the smallest number of decimal places in any of the given terms.
- For example, 12.34 + 2.006 - 8.9 = 5.4 because 8.9 has only one decimal place.
Significant Figures Rule #3
- Numbers that are not measured may be considered exact. Irrational numbers such as π and e are known to many significant figures and do not limit your results.
- For example, 1/3(4.56π) = 4.78 is reported to three significant figures because neither 1/3 nor π is measured, and our answer is limited only by the three significant figures of 4.56.
Significant Figures Rule #4
It is best to use scientific notation because a zero that acts as a placeholder is not necessarily a significant figure. For example, m = 390 kg may have two or three significant figures. To avoid that ambiguity, you may add a decimal point; for example, m = 309. kg has three significant figures. A better way to clarify the number of significant figures is to use scientific notation: m = 3.90 x 10² kg has three significant figures, and m = 3.9 x 10² kg has two significant figures.
Significant Figures Rule #5
You should keep extra significant figures intermediate steps when making a calculation, but you should round the final answer to the correct number of significant figures. The extra significant figures in an intermediate result help avoid introducing an error due to rounding a number up or down. This step is particularly important if an intermediate result is a number ending in 5.
Significant Figures Rule #6
When your answer begins with a 1, it is okay to keep one extra significant figure (as long as none of the operands has a leading 1). For example, 5/4.3 = 1.2
Estimate
It is not a guess; it is a calculation based on a few roughly known values.
Order of magnitude
A calculation based on values with no significant figures. Only the power of 10 is known.
Major concepts:
1. Scientific theories make testable predictions.
2. Scientific evidence comes from measured observations.
3. A standard unit is precisely defined quantity to which measurements are compared.
4. The SI system (Système International d'Unités) is a set of standard units used worldwide in the scientific community and in this textbook.
5. The terms uncertainty and error are used to describe the imperfection of a measurement.
6. The number of reported digits--known as the number of significant figures--implicity expresses the uncertainty of the measurement.
7. Mass density is p = m/V
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