Introduction to Physics Chapter 1

Some Terms  Science  The study of the natural world  Physics  The study of energy and matter and how they are related  Hypothesis  A possible explanation for a set of observations  Theory  A hypothesis that has been repeatedly tested and has yet to be shown to be false (attempts to explain why a law is)  These do change as new experiments are done and new data is collected, but they are not merely guesses, they do have some support  Law  A description of observable fact (a statement of what is, not why it is true)

The Scientific Method  Find a problem  Create a hypothesis  Must be a testable statement  Perform a controlled experiment  Only one thing can be changed at any given time (one variable)  Must have something to compare your results to (a control)  Dependent variable  The thing you measure in an experiment (responding)  Independent variable  The thing you change in an experiment (manipulated)

More Method  Collect data  Quantitative data  Data that can be counted or measured (a number)  Qualitative data  Data that is observed (a description)  Usually presented in the form of a table or graph  Formulate a conclusion  Decide whether the hypothesis is supported  Explain why you may have gotten the result that you did

More on Measurements  Scientists use the SI system of units so we can all communicate in the same language  Includes the metric system (m, g, l, etc) and other units (s, K, A, etc)  Accuracy  How close a measurement is to the correct answer  Precision  How reproducable a measurement is  Dimensional analysis  Converting between units using an equivalence statement

Significant Figures  When measuring with a device, you write all the readable digits and then estimate one uncertain digit to create the correct amount of significant figures (a measure of the preciseness of your measuring device)  When looking at a number, you find the sig figs with the following rules:  All non zeros are significant  Trapped zeros are significant (ex. 1001)  Trailing zeros AFTER a decimal are significant (ex )

Calculating with Sig. Figs.  When performing calculations, your answer can only be as precise as your weakest measurement  For adding or subtracting, your answer can only have as many numbers after the decimal as the number with the least  For multiplying or dividing, your answer can only have as many sig figs as the number with the least

Graphing Data  When graphing, the dependent variable goes on the y axis (vertical) and the independent variable goes on the x axis (horizontal)  Be sure to always include a title  Units and labels must be included for each axis  When numbering the axes, use consistent steps (ex. Go by 5’s, 10’s or 0.02’s)  Connect data points using a best fit line or curve (do not connect the dots)  These graphs can then be used as models to predict future outcomes or events

3 Main Graph Types  Linear  y = mx + b  The slope, m, indicates the ratio of change between the 2 factors  The 2 factors increase or decrease at the same rate  Quadratic  y = ax 2 + b + c  The dependent variable changes more quickly than the independent (dep. increases)  Inverse  y = a/x  The dependent variable changes more quickly than the independent (dep. decreases)