Introduction to Physics

Intro to physics  How do you feel about physics?  What are your impressions of it?  What are you excited about?  What are you nervous about?

Intro to physics  Physics is simply the study of the physical world  Any problem that deals with temperature, size, motion, position, shape, or color involves physics

Intro to physics  Areas within physics  Mechanics  Thermodynamics  Vibration and wave phenomena  Optics  Electromagnetism  Relativity  Quantum mechanics

Intro to Physics  Models are often used  Break things down

Intro to physics

 System - a single object and the items that immediately affect it  Hypothesis- a reasonable explanation for observation-one that can be tested with additional experiments

Measurements in experiments  Dimension- A description of what kind of physical quantity is represented by a certain measurement  Ex: length, mass, time, velocity, and force  Si units are used  Ex: Meter, gram, second  Sometimes it may appear as if a new unit is introduced but often times these units are just shorthand for a combination of units

Measurements in experiments

 Conversions review  How many meters is 37.2 millimeters  How many milligrams is 568 kilograms

Measurements in experiments  Dimensions and units must agree  TIP: A good way to check your work is to check that the units in your answer are appropriate for the dimension being sought  Best to convert numbers to the same unit(when possible) before doing any arithmetic

Measurements in experiments  Accuracy - the extent to which a reported measurement approaches the true value of the quantity measured  Precision -The degree of exactness or refinement of a measurement

Measurements in experiments

 Experimental work is never free of error  Error can be minimized by taking repeated measurements  Method error results when measurements are taken using different methods  Instrument error results when an instrument is not calibrated properly

Measurements in experiments  Precision  How exact a measurement can possibly be  Typically dependent on limitations of the measuring instrument  Not a result of human error or lack of calibration  Can improve precision by making a reasonable estimate

Measurements in experiments  A review of significant figures  All the certain digits plus one digit that is uncertain  When the last number in a recorded measurement is zero it can be difficult to tell whether the zero is there as a place holder of as a significant digit  Scientific notation comes in handy here!

Measurements in experiments  Sig fig rules 1. ALL non-zero numbers are significant Examples: 9.99 (3sf) (6sf) 2. Zeros between non-zero numbers are significant Examples: (5sf) (6sf) 3. Zeros before non-zero numbers are NOT significant Examples: (2sf) (3sf)

Measurements in experiments  Sig Fig rules continued 4. Zeros that are after a non-zero number AND after the decimal place are significant Examples: (5sf) (7sf) 5. Zeros after a non-zero number but to the left of the decimal place are NOT significant Examples: (2sf) 500 (1sf)

Measurements in experiments  When doing calculations your final answer and NEVER be more precise than the least precise measurement used  CALCULATORS DO NOT PAY ATTENTION TO SIG FIGS!!!!!!

Measurements in experiments Addition or Subtraction: Final answer has the same number of significant digits after the decimal place as the smallest number in the problem. Multiplication or Division: Final answer has the same number of significant figures as the number with the least significant figures in the problem.

The language of physics  Graphs and tables are a great way to organize and study data  From a graph a helpful equation can be gained

The language of physics  Many of the most important equations in physics do not contain numbers, they represent a simple description if the relationship between physical quantities  Letters are often used to describe specific quantities in an equation  Ex: Δ-difference or change in

The language of physics  Units are abbreviated with “regular letters” however variables or other specific quantities are boldfaced or italicized  The tables in appendix A can help keep track of abbreviations

The language of physics  Physics equations are valid only of they can be used to make predictions about situations

The language of physics  A car is moving at 88 km/h. You want to find out how long it will take it to travel 725 km.  Dimensional analysis-makes use of the fact that dimensions can be treated as algebraic quantities  Quantities only be added or subtracted if they have the same dimensions  The two sides of any given equation must have the same dimensions

The language of physics  A car is moving at 88 km/h. You want to find out how long it will take it to travel 725 km.  Dimensions of length over time

The language of physics  Order of magnitude calculations can be helpful in estimating your answer to know if you’re on the right track  This can also be helpful in estimating answers to problems where little information is given