In science there is only physics; all the rest is stamp collecting!

In science there is only physics; all the rest is stamp collecting!

• Ernest Rutherford

• (Ernest Rutherford was awarded a Nobel Prize in Chemistry)

“Physics is at the heart of all science”

• Allen Gandell 2003

• Allen Gandell has never won a Nobel prize

• BUT!!!!!!

• Allen Gandell did come close to winning an attendance award at cub scout camp!

Can you think???

• On a balance beam, we place the exact same mass of ice on both sides such that they balance evenly. One side is allowed to melt while the other stays frozen by magic.

• Which way will the scale tilt and why??• Given equal volumes of ice and water, instead of

mass, which way will it tilt??• Hint: in what way is water a unique compound?

What was called Natural Philosophy?

• Natural philosophy was the original name used by the early Greek “intelligencia” to describe what we call physics.

• It is simply an attempt to understand and describe nature intuitively and through mathematics,

• It is amazing how much of classical physics(nature), can be described with simple algebra!!

AP Physics

• Mr. Gandell

• Class meets every day all year

• If you are IB,you are in the wrong class

Mr. Gandell

• 10th Year at Stanton

• Professional Civil/Structural Engineer

• BSCE – McGill University (cum laude)*

• MSCE- Carleton University

Grades – 1st to3rd Nine Weeks

• 2 separate grades: AP Physics and Physics II

• AP Physics is weighted

• Physics II is now weighted for the first time.

AP Physics Grade

• Tests only – 500 total points

• 3-4 chapter tests each 9 weeks

• Comprehensive test at end of quarter. If higher than all of chapter tests – I will drop the low chapter test and count the comprehensive test twice

AP extra credit

• I have made science fair almost optional this year

• If you decide to participate it will count for extra credit in Physics II. This is the 1st ever time I am allowing extra credit. I think I’m getting old and senile!!

• Alternative: agree to tutor a physics I student 45 min per week.

Physics II Grade

• Based on a percentage of points of everything else: quizzes, labs, graded assignments etc.

• There will be a lab quiz each quarter

• Labs are very important to this grade!!

• Takes special effort to fail physics II!!!

Fourth 9 Weeks

• Daily Graded Review Quizzes

• Both grades based on a percentage of all available points. ie one test serves both grades!

Goals

• 80-90% pass AP test

• 30% or more “5’s” on AP Test

My Record

• 80%+ pass overall

• 99% of those that tried hard passed the AP!!!!!!

• 100% o those who tried hard passed the AP course!!!!!

• 99% of those who tried got an A in Physics II. !!!!

Test Dates

• AP Test

early in May

Time flies

AP Physics

• THIS can be a very HARD class or it can be survivable. How?

• 3 step plan??• Now is the time to

transfer if you are not dedicated to passing the AP test.

Curriculum Guide

• Refer to the curriculum guide

• Due back no later than Monday signed by you and a parent

• Contract?

Handouts

• Formula Sheets

• List of Constants

• Critical thinking

• Uncertainty lab & uncertainty definitions

This Year: Study Guide Required.

Homework

In the beginning there was only darkness.

• Chapter 1 Review

• Basic quantities and units

• % error calculations vs. uncertainty

• Dimensional analysis

• Conversions!!!!!!!

• Basic trig and math review

Do you remember???

• We measure a lot with a meter stick as 20m x 12m.

• Precision is ± ?

• % error is ______ %

• How many sq. meters can the area be off??

Fundamental Units of SI System

• Length – Meter

• Mass – Kilogram

• Time – Second

• Temperature - Kelvin

• Electrical Current – Ampere

• Mole: Avogadro’s # of something

• Luminous Intensity - Candela

Meter: Originally 1/ 10 millionth of distance from North Pole to equator on

meridian through Paris

Meter

• In 1889 the distance between 2 lines inscribed on a platinum – iridium alloy became the standard meter

• What is the problem with this being the standard?

• Length changes with temperature

Meter

• Today the meter is defined by the speed of light in a vacuum.

• A meter is the distance light travels in a vacuum in 1 / 299,792,458 seconds

What is the difference between mass and weight?

• Mass is a measurement of the amount of matter an object has. It gives matter a quality called_____________??

• Weight is the result of the interaction of a mass with a gravitational force

Mass• SI unit of Mass is the Kilogram

• Standard kilogram is a platinum – iridium cylinder kept in France.

• Copy number 20 is kept in USA at National Institute of Standards and Technology (NIST)

• Kilogram is only standard unit still defined by an artifact

Time

• Standard unit of time is the Second

• The standard second is defined as the time interval between the vibrations in the cesium atom used in atomic clocks

• 1 second = 9,192,631,770 vibrations

Fundamental vs Derived Units

• We will define the other fundamental units as we encounter them in class

• Derived units are formed from the fundamental units

• Example: meters per second

Significant Figures

• Appropriate for things that are measured

• There is no such thing as an EXACT measurement

• All measurements contain a degree of uncertainty

What is the difference between precision and accuracy?

• Precision: the degree of exactness to which a measurement can be reproduced

• Define precision for any measuring tool? The answer appears later. Can you find it?

• Accuracy: extent to which a measured value agrees with the standard value of a quantity

Precision vs. Accuracy

Uncertainty

• Because the precision of all measuring devices is limited – the number of digits that are valid for a measurement are limited

• Example: meter stick. The smallest increment is the millimeter. We can only estimate between the millimeter marks, there will be some uncertainty

• (1/2 smallest division!)• .The last digit in a measurement is the uncertain

digit

Rules for significant figures

• Non zero digits are significant

• All final zeros after the decimal place are significant

• Zeros between 2 other significant digits are significant

• Zeros used solely for spacing the decimal point are not significant

What is the difference between an error and an uncertainty?

• An error is a mistake. Can be avoided.

• An uncertainty is a limit to the precision of a measurement or calculation. Can’t be avoided, only minimized.

• Significant figures reflect precision. The results of a calculation cannot improve your precision

The quantity with the least number of significant figures will

determine the number of significant figures you may have

in your final answer!

Dealing with uncertainties

• Refer to the uncertainties handout.

• Remember measurements always contain a degree of uncertainty

Dealing with Uncertainty

• To obtain a more reliable result, a physical quantity is often measured a number of times

• Precision deals with our ability to reproduce measurements

Precision

• If we measure a length of a board 3 times and got 3.21 m, 3.22 m and 3.20 m – then our readings would be fairly precise.

• If we measured the board instead to be 3.21 m, 3.41 m and 2.81m – then our precision would be low

Accuracy of a measurement is its relation to its true or accepted

value

We should strive to be both accurate and precise in the lab.

Graphing Uncertainties

• Too often students will draw a graph in a lab write-up by simply connecting the data points

• Due to the uncertainties of measurement, this may prevent us from seeing the desired relationship of the graphed physical quantities

Graphing Uncertainties

• Data points should be marked with small circles or crosses. The uncertainty bars should then be added.

Graphing Uncertainties: then we can find the best fit line

Combining Uncertainties

• Combining Uncertainties – use rules on handout

• Ignoring uncertainties: when one of the uncertainties is less than a quarter of the other you can ignore it

Percent vs Absolute Error

• Absolute: real number with units.

• Eg: 3 meters + 2 cm.

• Percent : ratio of error to measure expressed as a percent.

• Eg : (.02m/3m)x 100%

Combining Uncertainties

• Shorthand rules

• + or – only absolutes add• X or ÷ only percentages add• Pure Numbers: When you multiply or divide by

pure numbers, you multiply or divide the absolute uncertainty by the pure number

Averaging Numbers with Uncertainties

• If the numbers share the same degree of uncertainty, the average will have that uncertainty

• If the numbers have different uncertainties, follow the rules for adding uncertainties and dividing by a pure number

Types of Coordinate Systems

• Cartesian

• Plane polar

Cartesian coordinate system

• Also called rectangular coordinate system

• x- and y- axes• Points are labeled

(x,y)

Plane polar coordinate system

• (r,) Origin and reference line are noted

• Point is distance r from the origin in the direction of angle , ccw from reference line

• Points are labeled

More Trigonometry

• Pythagorean Theorem• C2 = a2 + b2

• To find an angle, you need the inverse trig function– for example, Θ = sin-10.707 = 450

• Be sure your calculator is set appropriately for degrees or radians

Trigonometry Review

sin

cos

tan

opposite side

hypotenuse

adjacent side

hypotenuse

opposite side

adjacent side

Problem Solving Strategy

Are Girls faster than Boys?

• Can we use a penny and paper to answer this question?

• How accurate can we be?

• How precise can we be?

• How precise is our instrument?

• How reliable will our conclusion be?

Assignment

• You will make your own reaction measuring tape describing how to mathematically derive the distances between time demarcations.

• Allotted time : due when we do acceleration.

• You will then use your instrument to plan and execute a lab to test your theory. Due in 1 week after handing in instrument.

continued

• Your lab should be designed to illustrate and reinforce the understanding of precision, accuracy, error, and how we most often structure our procedure to minimize error and maximize precision.

• You must also explain in detail the fundamental equations that were used to design the instrument.

Homework

• Read Chapter 1• Probs: AP 3,12,40,44,45• Critical thinking• Review Handout on

Uncertainties• Lab presentation (next

slide)

• Curriculum Guides due back NLT Friday