WHAT IS PHYSICS, MEASUREMENT AND UNCERTAINTY? Topics 1.1 and 1.2 on IB Syllabus

What is Physics? What are the topics of Physics?

What does physics have to do with me? Discussion: Identify the area of physics that is most relevant to each of the following situations: 1.Lighting in your room 2.Listening to your favorite band 3.Wearing sunglasses 4.A soccer game 5.Cooking dinner

What range of sizes does the universe hold?  Powers of 10 Video  A power of 10 (10 2, 10 5, ) are called orders of magnitudes

Ranges:  Length: radius of the observable universe (13.7 billion light years) diameter of proton  Mass: total mass of observable universe mass of an electron Time: age of the universe passage of light across a nucleus

How do we measure and express measurement in physics? 1. Fundamental Units 2. Derived Units

1. Fundamental Units

2. Derived Units Examples:  A Newton:  A Watt:

How do we convert between units?  Convert a posted speed limit in the US of 55 miles/hour into  Meters per second  Kilometers per hour Helpful Conversions: 1.6 km/mile

SI Unit Prefixes:  See your textbook pg. 12 for common prefixes. How many kisses is 50 kilo kisses? What would you be if you earned 7 megabucks a year?

10 12 Microphones = 1 megaphone 500 millinaries = 1 seminary 2000 mockingbirds = 2 kilomockingbirds 10 cards = 1 decacards fish = 1 microfiche picolos = 10 9 los = 1 gigolo 10 rations = 1 decoration 10 millipedes = 1 centipede 2 snake eyes = 1 paradise 2 wharves = 1 paradox phones = 1 microphone 10 6 phones =1 megaphone mental = 1 centimental mate = 1 decimate bulls = 1 terabull boos = 1 picoboo bismol = 1 femtobismol

Measurement, Precision and Accuracy

How do we represent precision?

Significant Figures  The number of significant digits in a measured value indicates the precision of that measurement – a reading of g is more precise than a reading of 123 g. To determine the number of significant digits in a number:   read the number from left to right   the 1 st significant digit is the 1 st non-zero number you find   that digit and all that follow are significant provided there is a decimal point (if there is no decimal point and the number ends with 0’s, don’t count them)   in proper scientific form, all numbers in front of the  10 are significant  eg has 5 significant digits has ____ significant digits has ____ significant digits 400 has ____ significant digit 400. has ____ significant digits 4.0  10 2 has ____ significant digits

Calculations with Sig Figs  ADDITION RULE The sum of the numbers cannot be more precise than the least precise number. You do not really use significant digits.

Calculations with Sig Figs  The product cannot be greater than the number of significant figures in the factor having the fewest significant figures.

What is the difference between precision and accuracy?

Precision vs. Accuracy  Accuracy:  Precision:

Precision vs. Accuracy  Label each of the ducks with the either:  High Accuracy, High precision  High Accuracy, Low precision  Low Accuracy, High precision  Low Accuracy, Low precision

Precision vs. Accuracy

Systematic Errors… affect accuracy

The precision of the tool often determines the precision of data taken Compare these two measuring tools: What is the reading of the purple line? *** Always estimate to the smallest division plus one more decimal point

Random errors… affect precision.  Example: Three people time how long it takes to drop a ball from shoulder height.  Data:  Just because a tool is precise (timer) doesn’t mean that the measurements taken are precise. ground.  Even though a timer is precise, there is random error in this experiment, which affects precision.