PHYS 100 Chapter Notes - Chapter 1: Kilogram, English Units, Significant Figures
10 May 2018
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Chapter 1
Introduction
- Physics is concerned with describing the interactions of energy, matter, space and time
o Aims to describe the function of everything around us, from the movement of time
charged particles to the motion of people, cars and spaceships
- Application of physics
o Physics is useful in everyday situations as well as non-scientific professions
o Allows you to understand the hazards of radiation and evaluate these hazards more easily
- Models, Theories, Laws
o 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
o The laws are concise descrptions of the universe arouond us
▪ Human statements of the underlying laws of rules that all natural processes
follow.
o Model: Is a representation of something that is often too difficult to display directly
▪ Example is the planetary model of the atom
• Electrons are pictured orbiting the nucleus, analogous to the way planets
orbit the sun
• The mental image helps explain the observations we can make
o Theory: Explanation for patterns in nature that is supported by scientific evidence and
verified by various groups of researchers
▪ Include models to help visualize phenomena, whereas others do not
• Example: Newtons Theory of gravity, does not require a model because
we can observe the objects directly with our senses
• Kinetic Theory of gases is a model in which a gas is viewed as being
composed of atoms and molecules
o Law: Uses concise language to describe a pattern in nature that is supported by scientific
evidence and repeated experiments.
▪ Can be expressed in the form of a single mathematical equations
▪ Laws and Theories are both scientific statements that result from a tested
hypothesis and are supported by scientific evidence.
o If experiment does not verify the prediction, then the theory or law is wrong.
▪ Laws can never be known with absolute certainty because it is impossible to
perform every imagineable experiement to confirm a law in every scenario
▪ Physicists operate under the assumption that all scientific laws and theories are
valid until counterexample is observed
- The Scientific Method
o Scientists follow a process called the scientific method
▪ Begins with an observation and question that the scientist will research.
▪ Next the scientist performs some research about the topic and devises a
hypothesis
▪ Then the hypothesis is tested by performing an experiment
▪ Scientists analyzes the results of the experiment and draws a conclusion
o Classic Physics: Not an exact description of the universe but is an excellent
approximation under the following condition
▪ Matter must be moving at speeds less than 1% of the speed of light
▪ The objects dealt with must be large enough to be seen with a microscope
▪ Only weak gravitational fields, can be involved
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