Week 1 - Chapter 1 - Introduction of Science and Realm of Physics

Question 1

1What are the general truths of nature that science consists of?

Answer 1

Theories and Laws

We can only discover and understand them.

Question 2

What is concerned with describing the interactions of energy (electricity), matter (mass), space (distance), and time, and it is especially interested in what
fundamental mechanisms underlie every phenomenon?

Answer 2

Physics

Physics is the foundation of many important disciplines and contributes directly to others.

Question 3

What is a representation of something that is often too difficult (or impossible) to display directly?

Answer 3

A model

Newton’s theory of gravity does not require a model since we can observe it with our eyes.

However, the kinetic theory of gases, on the other hand, is a model in which a gas is viewed as being composed of atoms and molecules.
Atoms and molecules are too small to be observed directly with our senses—thus, we picture them mentally to understand what
our instruments tell us about the behavior of gases.

Question 4

What is an explanation for patterns in nature that is supported by scientific evidence and verified multiple times by various groups of
researchers?

Answer 4

A theory

Some theories include models to help visualize phenomena, whereas others do not. For example, Newton’s theory of Gravity does not require a model or mental image because we can observe the objects with our own senses.

Question 5

What uses concise language to describe a generalized pattern in nature and described the phenomena in nature and is supported by scientific evidence and repeated experiments?

Often, this can be expressed in the form of a single mathematical equation.

Answer 5

A law

Newton’s second law of motion
F=ma

Question 6

How are theories and laws similar?

Answer 6

Laws and theories are similar in that they are both scientific statements that result from a tested hypothesis and are supported by scientific evidence.

Question 7

How are theories and laws dissimilar?

Answer 7

The biggest difference between a law and a theory is that a theory is much more complex and dynamic.

A law describes a single action, whereas a theory explains an entire group of related phenomena. And, whereas a law is a postulate (a thing suggested or assumed as true as the basis for reasoning, discussion, or belief.) that forms the foundation of the scientific method, a theory is the end result of that process.

Question 8

What does the models, theories, and laws we devise sometimes imply?

Answer 8

The existence of objects and phenomena as yet unobserved

This is relevant to the discovery of black holes

Question 9

How do scientists inquire and gather information about the world?

Answer 9

Using a process called the scientific method

Question 10

What does the word physics mean and what did it encompass in ancient times?

Answer 10

Physics comes from Greek, meaning nature.

The study of nature came to be called “natural philosophy” and encompassed many fields, including astronomy, biology, chemistry, physics, mathematics, and medicine.

Over the last few centuries, the growth of knowledge has resulted in ever-increasing specialization and branching of natural philosophy into separate fields, with physics retaining the most basic facets.

Question 11

What did physics develop into from the Renaissance to the end of the 19th century? Why was it transformed?

Answer 11

Classical physics

It was transformed into modern physics by revolutionary discoveries made starting at the beginning of the 20th century.

Question 12

What are the Limits on the Laws of Classical Physics? (3)

Answer 12

For the laws of classical physics to apply, the following criteria must be met:

• Matter must be moving at speeds less than about 1% of the speed of light.
• The objects dealt with must be large enough to be seen with a microscope.
• Only weak gravitational fields (such as the field generated by the Earth) can be involved.

Question 13

What two revolutionary theories does Modern Physics consist of that is not a part of classical physics after the beginning of the 19th Century?

Answer 13

Relativity - must be used whenever an object is traveling at greater than about 1% of the speed of light or experiences a strong gravitational field such as that near the Sun.

Quantum mechanics - must be used for objects smaller than can be seen with a microscope.

Question 14

From what you are learned, what describes the behavior of small objects traveling at high speeds or experiencing a strong gravitational field?

Answer 14

Relativistic quantum mechanics

Question 15

What can all physical quantities can be expressed as combinations of? (4)

Answer 15

The four fundamental physical quantities:

• Length
• Mass
• Time
• Electric current

Question 16

How do we define a physical quantity? (2)

Answer 16

Either by:

• Specifying how it is measured or:
• Stating how it is calculated

For example, we define distance and time by specifying methods for measuring them (meters and seconds), whereas we define average speed by stating that it is calculated as distance traveled divided by time of travel (example km/h)

Question 17

What are the standardized values we use as measurements of physical quantities?

Answer 17

Units

For example, the length of a race, which is a physical quantity, can be expressed in units of meters (for sprinters) or kilometers (for distance runners).

Question 18

What are the two major systems of units used in the world called?

How were these two systems derived?

Answer 18

SI units and English units

English units were historically used in nations once ruled by the British Empire and still widely used in the US.

SI units are derived from the French Système International.

Question 19

Name the four fundamental physical quantities and their fundamental SI units.

Answer 19

Length = meters (m)

Mass = kilograms (kg)

Time = seconds (s)

Electric Current = amperes (A)

Question 20

What do you call physical quantities, such as force and electric charge, that are expressed as algebraic combinations of the four fundamental units (example, speed is length divided by time)?

Answer 20

Derived units

Question 21

Why is the metric system convenient? (2)

Answer 21

The metric system is convenient for scientific and engineering calculations because the units are categorized by factors of 10.

Units can be used over extremely large range of values by using the appropriate suffix.

Question 22

Metric System Practice (9)

Name the metric prefix

1. 10^15
2. 10^12
3. 10^9
4. 10^6
5. 10^3
   6 10^0
6. 10^ -2
7. 10^ -3
8. 10^ -6
9. 10^ -9
10. 10^ -12

They are indicative of how many zeroes the number has.

Answer 22

1. Peta
2. Tera
3. Giga
4. Mega
5. Kilo
6. No prefix; single unit!
7. Centi
8. Milli
9. Micro
10. Nano
11. Pico

Question 23

What is the order of magnitude?

Answer 23

This refers to the scale of a value expressed in the metric system. Each power of 10 represents a different order of magnitude.

For example, 800 = 8 x 10^2 and 450 = 4.5 x 10^2 which means both of these numbers belong to the same order of magnitude: 10^2

Order of magnitude can be thought of as a ballpark estimate for the scale of a value like the diameter of an atom and the diameter of the sun: 10^-9 vs. 10^9

Question 24

Unit Conversion and Dimensional Analysis (Review)

Let us say that we want to convert 80 meters (m) to kilometers (km).

1. List the units you have and the units you want to convert them to.
2. Determine a conversion factor relating meters to kilometers. conversion factor is a ratio expressing how many of one unit are equal to another unit.

For example, there are 12 inches in 1 foot, 100 centimeters in 1 meter, 60 seconds in 1 minute, and so on. In this case, we know that there are 1,000 meters in 1 kilometer.

3. Now we can set up our unit conversion. We will write the units that we have and then multiply them by the conversion factor so
   that the units cancel out

Note that the unwanted m unit cancels, leaving only the desired km unit. You can use this method to convert between any types
of unit.

See Flipside.

Answer 24

Question 25

What is how close a measurement is to the correct value for that measurement?

Answer 25

Accuracy

For example, let us say that you are measuring the length of standard computer paper. The
packaging in which you purchased the paper states that it is 11.0 inches long. You measure the length of the paper three times
and obtain the following measurements: 11.1 in., 11.2 in., and 10.9 in. These measurements are quite accurate because they are
very close to the correct value of 11.0 inches. In contrast, if you had obtained a measurement of 12 inches, your measurement
would not be very accurate.

Question 26

What of a measurement system refers to how close the agreement is between repeated measurements (which are repeated under the same conditions) called?

Answer 26

Precision

Consider the example of the paper measurements. The precision of the measurements refers to the spread of the measured values. One way to analyze the precision of the measurements would be to determine the range, or difference, between the lowest and the highest measured values.

In that case, the lowest value was 10.9 in. and the highest value was 11.2 in. Thus, the measured values deviated from each other by at most 0.3 in.

Question 27

What does the image model for precision and accuracy?

Answer 27

What does the image model for precision and accuracy?

Question 28

What does the degree of accuracy and precision of a measuring system relate to?

Answer 28

The uncertainty in the measurements. Uncertainty is a quantitative measure of how much your measured values deviate from a standard or expected value.

Question 29

In more general terms, what can be thought of as a disclaimer for your measured values?

Answer 29

Uncertainty

For example, if someone asked you to provide the mileage on your car, you might say that it is 45,000 miles, plus or minus 500 miles. The plus or minus amount is the uncertainty in your value. That is, you are indicating that the actual mileage of your car might be as low as 44,500 miles or as high as 45,500 miles, or anywhere in between.

Question 30

What denotes uncertainty in a measurement?

Answer 30

▲ or delta

For the paper exercise, since the length was measured with a maximum deviation of .2, it can be expressed as 11 in. ± 0.2

Question 31

What factors contribute to uncertainty in a measurement? (4)

Answer 31

1. Limitations of the measuring device
2. The skill of the person making the measurement
3. Irregularities in the object being measured
4. Any other factors that affect the outcome (highly dependent on the situation)

Question 32

What is percent uncertainty (%unc) defined as?

Answer 32

%unc = ▲A/A x 100%

Question 33

What is the method of adding percents for percent uncertainty mean for multiplication or division?

Answer 33

If measurements going into the calculation have small uncertainties (a few percent of less), then the method of adding percents can be used for multiplication or division.

This method says that the percent uncertainty in a quantity calculated by multiplication or division is the sum of the percent uncertainties in the items used to make the calculation.

For example, if a floor has a length of 4.00 m and a width of 3.00 m , with uncertainties of 2% and 1%, respectively, then the area of the floor is 12.0 m^2 and has an uncertainty of 3%. (Expressed as an area this is 0.36 m^2, which we round to 0.4 m^2 since the area of the floor is given to a tenth of a square meter.)

Question 34

What is so important about the preciseness of a measuring tool?

Answer 34

The more precise and accurate the measurements will be.

Question 35

What is the method of significant figures?

Answer 35

The rule is that the last digit written down in a measurement is the first digit with SOME uncertainty.

Significant figures indicate the precision of a measuring tool that was used to measure a value.

Question 36

What are the special considerations given to zeroes when calculating significant digits?

Answer 36

1. Zeroes sandwiched between significant digits are significant.
2. Zeroes that come before all non-zero digits are never significant (not sandwiched).
3. Zeros that come AFTER nonzero digits however…

• Zeroes that come after non-zero numbers WITHOUT a decimal are not significant. (always ask yourself if there is a decimal point)
• Zeros that come after non-zero numbers WITH a decimal point are significant.

Question 37

What is important to consider when combining measurements with different degrees of accuracy and precision?

Answer 37

The significant digits in the final answer can be NO GREATER than the number of significant digits in the least precise measured value.

Question 38

What are the two different rules when determining how many significant digits you can have with multiplication/division and addition/subtraction?

Answer 38

Multiplication/division - The result should have the same number of significant figures as the quantity having the least significant figures entering into the calculation.

Addition/subtraction - The answer can contain NO MORE decimal places than the least precise measurement.

Question 39

What is a skill that requires you to make a guestimate for a particular quantity and this skill is developed by thinking more quantitatively?

Answer 39

Approximation