The Language of Physics Pearland ISD Physics Mark Lesmeister

Objectives Interpret data in tables and graphs. Distinguish common symbols used in equations. Recognize common equations and graphs. Convert units. Use dimensional analysis.

Tools to make data easier to understand. Tables Very useful for displaying data precisely. The relationship between the quantities may not be clear. Graphs Visually display the relationship between two quantities. The precision of the data is limited by the scale of the graph.

Tools to make data easier to understand. Equations Mathematically display the relationship between two quantities. Can be manipulated using algebra:

Relating equations and graphs

Symbols used in physics equations S means “sum” or “total.” D means “difference” or “change in.” Quantity Symbol Units Unit Abbrev. Change in position Dx , Dy meters m Time interval Dt seconds s Mass kilograms kg

Evaluating physics expressions Units are treated like other algebraic quantities in equations. Ex.: A car travels 20 m/s for 120 s. How far does the car travel?

Dimensional analysis Dimensional analysis- determining what units would result from a calculation. In order to be correct, a calculation must produce units of the proper dimension. Ex.

Order of Magnitude Calculations Order of magnitude calculations are estimates made using orders of magnitude, that is, powers of 10. Ex.- How long is PHS, as an order of magnitude?

Converting units To convert units, multiply the quantity you wish to convert by fractions equalling one; that is, fractions with equivalent units in the numerator and denominator. For example, convert 20 m/s to km/hour.