Intro to Physics

Science is the study of nature’s rules.

The Basic Science-Physics

• Physics is the most basic of all the sciences.

• Physics is about the nature of basic things, such as:– Motion and Forces – Energy– Heat– Sound and Light– Matter and Composition of atoms.

Mathematics-The Language of Science

When the ideas of science are expressed in mathematical terms, they are unambiguous (clear).

Physics equations are systems of relationships.

SI Units

• Different units of measurement are used for different concepts.– Ex: seconds is for time

• Scientists have agreed upon 7 base units, called SI units for “System Internacional”

Metric Prefixes

• Prefixes are used to change SI units by powers of 10

• The main prefixes used in this course are kilo, hecta, deka, deci, centi, and milli

King Henry Died While Drinking Chocolate Milk

Check Your Understanding

How many meters (m) are in 3 kilometers (km)?

3000 meters or 3000 m. Just move the decimal point three to the right.

How many grams (g) are in 1,000 centigrams (cg)?

10 grams or 10g. Just move the decimal point 2 spaces to the left.

The Scientific Method

• Making observations, doing experiments, and creating models or theories to try to explain your results or predict new answers form the essence of a scientific method.

Scientific method:Scientific method: an orderly an orderly method for gaining, organizing and method for gaining, organizing and applying new knowledgeapplying new knowledge

1. Recognize the problem2. Make a hypothesis about the answer

Hypothesis:Hypothesis: an educated guess an educated guess3. Predict the consequences of the

hypothesis4. Perform experiments to test the

predictions5. Formulate the simplest general rule that

organizes the three main ingredients1. Hypothesis2. Prediction3. Experimental outcome

The Scientific Attitude

• In science, data and observations are based on facts to eliminate subjectivity.

Fact:Fact: a close agreement between competent a close agreement between competent observers who make a series of observations observers who make a series of observations of the same phenomenonof the same phenomenon

• Laws and principles are based on repeatable observations that have withstood the test of time and rarely, if ever, change.

Law or Principle:Law or Principle: A hypothesis that has A hypothesis that has been tested over and over again and is not been tested over and over again and is not contradictedcontradicted

• Theories are not fixed, but rather they undergo change.

Theory:Theory: a synthesis of a large body of a synthesis of a large body of information that encompasses well-information that encompasses well-tested and verified hypothesestested and verified hypotheses

• Theories undergo change when there is solid experimental evidence to the contrary.

** The refinement of theories is a strength of science, not a weakness**

Scientific Hypotheses Must be Testable

• A scientific hypothesis must be TESTABLE.

• It is more important that there be a means of proving a scientific hypothesis WRONG, rather than there be a means of proving it right.

Example 1

The alignment of the planets in the sky determines the best time for making decisions.

This hypothesis cannot be proven WRONG, nor can it be proven right.

This hypothesis is NOT SCIENTIFIC.

Example 2

Intelligent life exists on other planets somewhere in the universe.

Although this hypothesis can be proven correct by finding a single instance of intelligent life elsewhere in the universe, there is no way of proving it WRONG if no life is ever found.

This hypothesis is NOT SCIENTIFIC.

Which of these is a scientific Which of these is a scientific hypothesis?hypothesis?

1.1. Atoms are the smallest particles of Atoms are the smallest particles of matter.matter.

2.2. The universe is surrounded by a The universe is surrounded by a second universe, the existence of second universe, the existence of which cannot be detected by which cannot be detected by scientists.scientists.

3.3. Albert Einstein was the greatest Albert Einstein was the greatest physicist of the twentieth century.physicist of the twentieth century.

The answer is #1 because it is the only statement that can be proven wrong.

Check Your UnderstandingCheck Your Understanding

Accuracy vs. Precision

• When a measurement is made, the results often are reported with an uncertainty.

• Therefore, before fully accepting a new data, other scientists examine the experiment, looking for possible sources of errors, and try to reproduce the results.

• A new measurement that is within the margin of uncertainty confirms the old measurement.

Accuracy: A characteristic of a measured value that describes how well the results line up with the accepted value.

• How close a measurement is to the real value.• Ex: making a basket, nothing but net

Precision: A characteristic of a measured value describing the exactness of a measurement.

• how replicable a measurement is.• Ex: hitting the same place on the backboard

every time.

Graphing Data

• A variable is any factor that might affect the behavior of an experiment– Independent and dependent

Independent Variable: the factor that is changed or manipulated during the experiment

Dependent Variable: the factor that depends on the independent variable

• Independent variables are always on the x-axis of a graph

• Dependent variables are always on the y-axis of a graph

Check Your Understanding

Check Your Understanding

Which variable is the independent variable? How can you tell?

Mass is the independent variable because it is on the x-axis and it effects the length of the spring.

What is the SI unit for mass? For length?Mass is kilograms and length is meters.

Graphing Relationships• There are 2 main types of graphing

relationships:– Directly proportional

• Has a positive slope• Both variables increase• Both variables decrease• They do the same thing

– Inversely proportional• Has a negative slope• One variable increases as the other decreases• They do opposite things

Check Your Understanding

Which type of relationship is shown in the graph? How can you tell?

It is directly proportional. As the mass increases, so does the length.