1.1 Physics: An Introduction

Examples of how a model works in limited situations:

- An example is the planetary model of the atom in which electrons are pictured as orbiting the nucleus, analogous to the way planets orbit the Sun. We cannot observe electron orbits directly, but the mental image helps explain the observations we can make, such as the emission of light from hot gases (atomic spectra). - Physicists use models for a variety of purposes. For example, models can help physicists analyze a scenario and perform a calculation, or they can be used to represent a situation in the form of a computer simulation.

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

- Chemistry, for example—since it deals with the interactions of atoms and molecules—is rooted in atomic and molecular physics. - Most branches of engineering are applied physics. - In architecture, physics is at the heart of structural stability, and is involved in the acoustics, heating, lighting, and cooling of buildings. - Parts of geology rely heavily on physics, such as radioactive dating of rocks, earthquake analysis, and heat transfer in the Earth. - Some disciplines, such as biophysics and geophysics, are hybrids of physics and other disciplines. - Physics has many applications in the biological sciences. On the microscopic level, it helps describe the properties of cell walls and cell membranes (Figure 1.6 and Figure 1.7). On the macroscopic level, it can explain the heat, work, and power associated with the human body. - Physics is involved in medical diagnostics, such as x-rays, magnetic resonance imaging (MRI), and ultrasonic blood flow measurements. - Medical therapy sometimes directly involves physics; for example, cancer radiotherapy uses ionizing radiation. - Physics can also explain sensory phenomena, such as how musical instruments make sound, how the eye detects color, and how lasers can transmit information.

Theories examples:

- Newton's theory of gravity, for example, does not require a model or mental image, because we can observe the objects directly with our own senses. - 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.

Why is Physics important to daily situations:

- help you understand how microwave ovens work, why metals should not be put into them, and why they might affect pacemakers. - Physics allows you to understand the hazards of radiation and rationally evaluate these hazards more easily. - Physics also explains the reason why a black car radiator helps remove heat in a car engine, - it explains why a white roof helps keep the inside of a house cool. - operation of a car's ignition system - the transmission of electrical signals through our body's nervous system

More info on classical Physics...

- is not an exact description of the universe, but it is an excellent approximation under the following conditions: 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, and only weak gravitational fields, such as the field generated by the Earth, can be involved. - Because humans live under such circumstances, classical physics seems intuitively reasonable, while many aspects of modern physics seem bizarre. - This is why models are so useful in modern physics—they let us conceptualize phenomena we do not ordinarily experience. - We can relate to models in human terms and visualize what happens when objects move at high speeds or imagine what objects too small to observe with our senses might be like. - For example, we can understand an atom's properties because we can picture it in our minds, although we have never seen an atom with our eyes. New tools, of course, allow us to better picture phenomena we cannot see. In fact, new instrumentation has allowed us in recent years to actually "picture" the atom.

What is the Scientific Method?

A logical, systematic approach to the solution of a scientific problem

Step 4 of Scientific Method:

Finally, the scientist analyzes the results of the experiment and draws a conclusion. Example: You observe that the oil is at an acceptable level, and you thus conclude that the oil level is not contributing to your car issue. To troubleshoot the issue further, you may devise a new hypothesis to test and then repeat the process again.

Limits on the Laws of Classical Physics:

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, and only weak gravitational fields (such as the field generated by the Earth) can be involved.

Differences between laws and theories:

Law: is reserved for a concise and very general statement that describes phenomena in nature, such as the law that energy is conserved during any process, or Newton's second law of motion, which relates force, mass, and acceleration by the simple equation F=ma - Basically, a law is single action. They postulate (suggest) theory or idea of scientific method Theories: less concise statement of observed phenomena. For example, the Theory of Evolution and the Theory of Relativity cannot be expressed concisely enough to be considered a law. The biggest difference between a law and a theory is that a theory is much more complex and dynamic. - Basically, a theory is a group of related phenomena. Its end result of scientific method

However, if experiment does not verify our predictions, then the theory or law is wrong, no matter how elegant or convenient it is. Why is this?

Laws can never be known with absolute certainty because it is impossible to perform every imaginable experiment in order to confirm a law in every possible scenario. Physicists operate under the assumption that all scientific laws and theories are valid until a counterexample is observed. If a good-quality, verifiable experiment contradicts a well-established law, then the law must be modified or overthrown completely.

Principals?

Less broadly applicable statements. Example: Pascal's Principal, only applicable in fluids. Distinction between laws and principles often is not carefully made.

Physics was not always a separate and distinct discipline. It remains connected to other sciences to this day. The word physics comes from Greek, meaning nature. The study of nature came to be called "natural philosophy." From ancient times through the Renaissance, natural philosophy 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. (See

Classical Physics?

Physics as it developed from the Renaissance to the end of the 19th century

Such laws are intrinsic to the universe; humans did not create them and so cannot change them. We can only discover and understand them. Their discovery is a very human endeavor, with all the elements of mystery, imagination, struggle, triumph, and disappointment inherent in any creative effort...

The cornerstone of discovering natural laws is observation; science must describe the universe as it is, not as we may imagine it to be.

The models, theories, and laws we devise sometimes imply the existence of objects or phenomena as yet unobserved.

These predictions are remarkable triumphs and tributes to the power of science. It is the underlying order in the universe that enables scientists to make such spectacular predictions.

Step 1 of Scientific Method:

This process typically begins with an observation and question that the scientist will research. Example: Let us say that you try to turn on your car, but it will not start. You undoubtedly wonder: Why will the car not start?

Model?

a representation of something that is often too difficult (or impossible) to display directly. While a model is justified with experimental proof, it is only accurate under limited situations.

Models, Theories, and laws:

are used to help scientists analyze the data they have already collected. However, often after a model, theory, or law has been developed, it points scientists toward new discoveries they would not otherwise have made.

Role of Physics in Smartphone technology...

describes how electricity interacts with the various circuits inside the device.

Role of Physics in GPS system...

describes the relationship between the speed of an object, the distance over which it travels, and the time it takes to travel that distance. When you use this device in a vehicle, it utilizes these physics equations to determine the travel time from one location to another.

Physics can improve your problem-solving skills. Furthermore, physics has retained the most basic aspects of science, so it is used by all of the sciences, and the study of physics makes other sciences _____ to understand.

easier

Theory?

is an explanation for patterns in nature that is supported by scientific evidence and verified multiple times by various groups of researchers. Some theories include models to help visualize phenomena, whereas others do not.

Physics?

is concerned with describing the interactions of energy, matter, space, and time, and it is especially interested in what fundamental mechanisms underlie every phenomenon. The concern for describing the basic phenomena in nature essentially defines the realm of this field.

Classical Physics was transformed into ______ Physics by the beginning of the 20th century

modern

Physics aims to describe the function of everything around us, from the movement of tiny charged particles to the motion of people, cars, and spaceships. In fact, almost everything around you can be described quite accurately by the laws of _____.

physics

Step 2 of Scientific Method:

scientist typically performs some research about the topic and then devises a hypothesis. Example: First off, you may perform some research to determine a variety of reasons why the car will not start.

Step 3 of Scientific Method:

the scientist will test the hypothesis by performing an experiment. Example: State hypothesis, For example, you may believe that the car is not starting because it has no engine oil. To test this, you open the hood of the car and examine the oil level.

Similarity between law and theory:

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

Law?

uses concise language to describe a generalized pattern in nature that is supported by scientific evidence and repeated experiments. Often, a law can be expressed in the form of a single mathematical equation.