Physics 214 Physics of everyday phenomena

Physics 214 Physics of everyday phenomena Professor David H Miller Office room 376

[email protected]

Course Web site http://www.physics.purdue.edu/academic_programs/courses/phys214/

Announcements, Syllabus, schedule, Lecture notes, practice exams Lists lecture schedule Times and place of the two evening exams Deadlines for Homework and Concept questions Useful information Undergrad Office Room 144, Questions, Handouts

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Physics 214 Summer2014

1

This Week • Introduction Syllabus, CHIP, Help schedule • Grading Exams, Homework Concept questions • General Who am I, our Universe (just as an intro) • Lecture Ch 1,2 Straight line motion • Tsunamis

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The Book Book : Physics of Everyday Phenomena 5th, 6th, 7th or 8th edition. The 5th, 6th, 7th, editions will be much cheaper.

OVERVIEW OUTLINE CHAPTER MATERIAL SUMMARY QUESTIONS/EXERCISES HOME EXPERIMENTS AND OBSERVATIONS

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Course Outline  The lecture schedule and reading assignments are shown in the syllabus.  There will be two one hour evening exams and a two hour final  We want to make sure you get all the help you need and the ways to do this are detailed in the syllabus

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Reading and Problems It is very important that you  Read all the chapter material  work some questions, exercises and problems  Answers are in appendix d for: Questions Every 6th question starting with #3 Exercises Odd numbered Problems Odd numbered  Lectures for the whole summer will be posted on the Web before the summer session starts

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CHIP (Computerized Homework in Physics) There are 20 Homework assignments. First one is due by noon on Monday June 23rd There are 21 Concept assignments the first is due Wed June 25th IMPORTANT Read the QUICK GUIDE TO CHIP handout and login to the CHIP site today and make sure your Career ID and password work. There is a much longer guide to CHIP that you can access from the course home page. You must also register the serial number of your I Clicker in the student grade book of CHIP It is very unlikely that there are any errors in CHIP if it will not accept your answer then you have made an error. Most common errors are Wrong answer, Significant figures, Wrong sign

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Getting Help We will provide help by email and by scheduled sessions on SKYPE. You can also set up individual SKYPE or telephone calls by sending an email Specific information will be posted on the Web site.

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Plus Minus Grading We will be using the Plus Minus grading system

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A+,A

4.0

A-

3.7

B+

3.3

B

3.0

B-

2.7

C+ 2.3 C 2.0 C1.7 D+ 1.3 D 1.0 D0.7 E, F, WF, EF, IF


0.0

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Who am I Originally from England I’m an experimentalist in High Energy or Elementary Particle Physics trying to find/understand  The physical laws which govern the Universe  The fundamental building blocks of all matter  The evolution of the Universe from the Big Bang to the present day, 13.6 billion years later We use  Particle accelerators which produce collisions with energy densities the same as a billionth of a second after the big bang.

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Large Hadron Collider The worlds highest energy collisions in Geneva, Switzerland. 18 miles in circumference with 800,000 liters of liquid Helium (the coldest place in the entire Universe) Proton

Proton

E=mc2 Energy density same as a billionth of a second after the Big Bang which produces the building blocks of our Universe

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Higgs Boson You may have seen a lot of publicity concerning the discovery of what is probably the Higgs boson and the Higgs field which gives mass to all particles. Just as the gravitational field gives weight to an object and the Electromagnetic field makes two magnets “heavy” by pulling them together or pushing them apart the Higgs field permeates the whole Universe and interacts with all particles to give them mass. Our picture of how objects interact is by having particles exchanged, like throwing a football back and forward So every field has an associated particle . The Higgs particle is about 125 times the mass of the proton and required very high energy to produce it at the Large Hadron Collider 5/21/2014


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This week Our Universe • Our World • How do we measure quantities • Describing moving objects • Tsunami’s

•

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What is Physics Physics is the study and understanding of all the physical phenomena That we see in our everyday life At very small distances, atoms, nuclei, quarks… At extreme energies – Big Bang At extreme velocities - relativity On earth and throughout the Universe and back in time to 13.7 billion years ago – Hubble, Cobe, WMAP We are able to explore and understand the whole Universe from a billionth of a second after the big bang to today and also predict the future 5/21/2014


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Experiment and theory Our knowledge is based on experiments which are reproducible.  We develop mathematical theories which agree with experiment and generally predict new phenomena. Experimentalists are not constrained by the theory and continue to examine our Universe from 10-17m to 13 billion light years and from t = “0” to 13.7 billion years later. any new theory must agree with all previous experimental observations. A theory is a mathematical consistent framework for the interpretation of all accumulated knowledge. It is like looking at a partially painted picture and determining what the finished picture would depict.

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Physics of the Universe We only have one planet We only have one Universe Current understanding is always based on the simplest explanation that fits the facts (no aliens!!) Experimental measurements always have errors Forefront science is very difficult and incorrect results do occur which are then corrected

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Where are we? Light Year: the distance that light travels in one year (9.46 x 1017 cm). 186282x365.242x24x3600x5280x30.48 1.86282x105x3.65242x102x24x3.6x103x5.280x103x30.48

The nearest star (other than the sun) is 4.3 light years away. Our Galaxy (the Milky Way) with 100 billion stars is about 100,000 light years in diameter. Number of stars in the Universe is ~ 1028 5/21/2014


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Framework

Underlying principles Physics is the same everywhere Fundamental constants and physical laws have not changed over the age of the Universe Observations We can create conditions in the lab which existed a billionth of a second after the big bang. We can understand how our Universe evolved over 13 billion years and actually observe the evolution of the Universe

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Forces and Particles Fundamental forces are what has shaped the Universe and are responsible for all the phenomena we see in our everyday life. There are only 5 forces Strong Force – holds the protons and neutrons of the nucleus together Weak Force – responsible for radioactive decay Electromagnetic force – Holds electrons in atoms, electrical currents, magnetism, light Gravitation - Attractive force between objects, solar system Dark Energy – mysterious force expanding space 5/21/2014


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Structure and Forces Gravitation F

Strong Force

Solar system galaxies objects falling

Electric charge F F F

everything not gravity biology photosynthesis

Weak Force

cars, planes

+ electron Common carrier of electric charge and electric current is the electron 5/21/2014

Neutron Proton Radioactive decay Physics 214 Summer2014

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Building blocks Building blocks Quarks – up, down, strange, charm, beauty,top Leptons - electron, muon, tau, 3 neutrinos Force carriers – γ, g, W, Z Missing pieces Building blocks – Higgs, supersymmetry… Questions – Dark energy, dark matter….. Speculation – parallel universes, extra dimensions..

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The Universe

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Large scale structure

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The Universe at 300,000 years

2.70 K relic radiation from 300,000 years after the big bang 5/21/2014


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Observation and Everyday life In our everyday life one can make observations and ask why? The fundamental physical laws and in particular forces are responsible for all the phenomena we observe. As we go through the semester I will discuss and explain everyday physics topics. I encourage you to ask questions on any topic or send me an email with your question and I’ll answer and also discuss the topic in class if it is of general interest

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Fundamentals As we observe the world around us we need to describe it in the language of mathematics. We need the fundamental quantities Length (distance) Time Coordinate system (reference point, direction, clock) Mass ( so much of something)

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Units and definitions Over the few thousand years of science there have been many systems of units but the system of choice is the SI system http://unicon.netian.com/unitsys_e.html SI Length – hand, foot, mile,… meter Time – sundial, water clock, second Direction – north, south, east, west cartesian Mass – pound, ton, gram… kilogram Volume – peck, bushel, cup … cubic meter Area - acre, square mile, hectare square meter

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Consistency We always need to use consistent units so that in equations such as A = B + C the quantities A, B, C have the same units. We may need to convert units to be consistent Your answers to problems must also have units. You do not always have to convert to SI units. For example if you travel 60 miles in two hours then your average speed is 30 miles per hour and you do not convert to meters/second unless you are specifically asked to do so.

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Conversions, prefixes and scientific notation giga

1,000,000,000

109

billion

1 in

2.54cm

mega

1,000,000

106

million

1cm

0.394in

kilo

1,000

103

thousand

1ft

30.5cm

centi

1/100

10-

hundredth

1m

39.4in

thousandth

1km

0.621mi

1mi

5280ft

1.609km

1lb

0.4536kg

g =9.8

1kg

2.205lbs

g=9.8

0.01

3.281ft

2

milli

micro

1/1000

0.00 1

1/1,000,000

1/106

103

10-

millionth

6

nano

1/1,000,000,000

1/109

10-

billionth

9

Appendix b 5/21/2014


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Average speed Average speed = distance/time s = d/t = 260/5 = 52mph Units meters/second kilometers/second miles/hour feet/second Average speed is a positive number 52mph = 52x5280/3600 = 76.26666666 = 76.27 feet/sec (60mph = 88ft/sec) 5/21/2014


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Instantaneous speed Instantaneous speed is what you see on your speedometer. This is the average speed for a very short time interval s = d/∆t We can plot speed versus time and obtain a graph which has all the information for the journey moviecar

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Vector quantities In addition to knowing average speed or instantaneous speed we need to know the direction. The quantity giving both speed and direction is the velocity. Velocity is an example of a vector quantity and is represented in a “picture” by an arrow giving the direction and the length of the arrow proportional to the magnitude. Velocity Acceleration Force momentum

Appendix c To specify direction we need a coordinate system 5/21/2014


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Coordinate systems We live in a three dimensional world so the general coordinate system uses three axes at right angles x,y,z. We will use coordinate systems in one or two dimensions

-

+x

N W

y + E

-

x

-

S 5/21/2014

+


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The earth as a coordinate system and Maps We live on a sphere but most maps are flat and this increases the apparent size of countries as one moves further from the equator 1 nautical mile = 1/21600 of the circumference of the earth at the equator 1 knot = 1 nautical mile per hour 1.1508 miles/hour 1 kilometer = 1/10,000 the distance from the North Pole to the equator passing through Paris

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Motion in a straight line

-

d

d is the distance from the start point it is NOT necessarily the total distance traveled

+ x

2

3

4

1

1 Constant velocity + 2 Stopped 3 Constant velocity + 4 Constant velocity 5/21/2014


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Acceleration

A change in velocity is called acceleration a = change in velocity/elapsed time a = ∆v/t Average acceleration t is “large” Instantaneous acceleration a = ∆v/ ∆t Acceleration is a vector with direction defined by ∆v units are length/(time x time) meters/sec/sec miles/hour/hour feet/sec/sec ∆v = vfinal – vinitial can be + or –

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Straight line motion Constant acceleration

or

v = v0 + at (definition of acceleration) “red area” = v∆t = distance traveled in ∆t d = v0t + 1/2 ∆v t but since a = ∆v/t d = v0t + 1/2at2 (d is distance from start) d = 1/2(v + v0) t (average speed times t)

http://www.physics.purdue.edu/class/applets/phe/acceleration.htm 5/21/2014


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General case of acceleration Acceleration occurs when the velocity changes in magnitude or direction or both. In the first example shown if the magnitude of v does not change we have uniform circular motion and the acceleration vector points toward the center of the circle.

a

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Straight line motion 100 meter track event

d

a

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Velocity and acceleration

-

d

+ x

Remember v = ∆d/∆t a = ∆v/∆t So the magnitude of a is not related to the magnitude of v and the direction of a is not related to the direction of v v = 0 a = + accelerating from rest v = 0 a = - reversing from rest (speed increasing) v = + a = + increasing velocity v = + a = - decreasing velocity v = - a = + slowing down v = - a = - speeding up in the – x direction 5/21/2014


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Graphs For a specific journey even with variable acceleration one can determine everything about the journey, that is d,v,a as a function of time from A distance versus time graph Or A velocity versus time graph (except the start point) Or An acceleration versus time plot (except the start velocity or the start point) 5/21/2014


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Summary Chapters 1 and 2

-

d

+ x

Units----Length, mass, time SI units m, kg, second Coordinate systems Average speed = distance/time = d/t Instantaneous speed = d/∆t Vector quantities---magnitude and direction Velocity----magnitude is speed Acceleration = change in velocity/time =∆v/∆t

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One dimensional motion constant acceleration 1) v = v0 + at velocity changes by the amount a every second 2) d = v0t + 1/2at2 d is the distance from the start point at t = 0 3) d = 1/2(v + v0) t 1/2(v + v0) is the average velocity Put t = 2d/ (v + v0)

into v = v0 + at

4) v2 = v02 + 2ad

There are only two independent equations

Drag race v0 = 0 v = 2d/t 5/21/2014


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Tsunami To put the recent Tsumami in perspective we can look at the evolution of the earth for the last 250 million years

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Current plate movements Notice the position of the Indian Subcontinent today. It moved hundreds of miles in 135 million years at a great speed (4 inches per year!!!) The Indian plate crashed into the Eurasian plate with such speed and force that it created the tallest mountain range on Earth, the Himalayas http://www.scotese.com/futanima.htm

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Origin and Destruction

A massive change in the sea floor maybe over hundreds or a thousand miles displaces a very large volume of water and generates strong disturbances as the water tries to reach equilibrium As the tsunami crosses the deep ocean, its length from crest to crest may be a hundred miles or more, and its height from crest to trough will only be a few feet or less. They can not be felt aboard ships nor can they be seen from the air in the open ocean. In the deepest oceans, the waves will reach speeds exceeding 600 miles per hour (970 km/hr). When the tsunami enters the shoaling water of coastlines in its path, the velocity of its waves diminishes and the wave height increases. It is in these shallow waters that a large tsunami can crest to heights exceeding 100 feet (30 m) and strike with devastating force.

tsunami.mov 5/21/2014


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Mega Tsunami’s Around the world there are accumulations of material from the ocean floor called chevrons that could have been deposited by giant waves after a meteorite impact. Some of these have been linked to impact craters on the ocean floor. Such waves would have been 1000 feet high!!

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Questions Chapter 2 Q8 A car traveling around a circular track moves with constant speed. Is this car moving with constant velocity No, the direction is changing

Q9 A ball is thrown against a wall and bounces back toward the thrower with the same speed as it had before hitting the wall. Does the velocity of the ball change in this process? Explain. Yes, it changes direction

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Q10 A ball attached to a string is whirled in a horizontal circle such that it moves with constant speed. a. Does the velocity of the ball change in this process? Explain. b. Is the acceleration of the ball equal to zero? Explain. The velocity changes direction so there is acceleration

Q11 A ball tied to a string fastened at the other end to a rigid support forms a pendulum. If we pull the ball to one side and release it, the ball moves back and forth along an arc determined by the string length. A. Is the velocity constant in this process? Explain. B. Is the speed likely to be constant in this process? What happens to the speed when the ball reverses direction? A Both magnitude and direction change. B The speed is zero 5/21/2014


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Q15 A car just starting up from a stop sign has zero velocity at the instant that it starts. Must the acceleration of the car also be zero at this instant? Explain. The acceleration is not zero, if it was the car would not move

Q17 A racing sports car traveling with a constant velocity of 100 MPH due west startles a turtle by the side of the road who begins to move out of the way. Which of these two objects is likely to have the larger acceleration at that instant? Explain. The car has zero acceleration but the turtle has acceleration

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Q18 In the graph shown here, velocity is plotted as a function of time for an object traveling in a straight line. A. Is the velocity constant for any time interval shown? Explain. B. During which time interval shown does the object have the greatest acceleration? Explain.

v

2

4 6 8 t (secs) A Yes from 0 – 2 seconds B From 2 – 4 seconds 5/21/2014


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Q19 A car moves along a straight line so that its position (distance from some starting point) varies with time as described by the graph shown here. 1. Does the car ever go backward? Explain. 2. Is the instantaneous velocity at point A greater or less than that at point B? Explain. 1 Yes in the last part 2 Greater at A

d B A t

Q20 For the car whose distance is plotted against time in Q19, is the velocity constant during any time interval shown in the graph? YES 5/21/2014


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Q28 A car traveling in the forward direction experiences a negative uniform acceleration for 10 seconds. Is the distance covered during the first 5 seconds equal to, greater than, or less than the distance covered during the second 5 seconds? Explain. If the car is always moving in the forward direction then it’s speed is higher in the first 5 seconds so the distance covered is greater

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Ch 2 #8

-

d

+ x

Car travels with a speed of 25 m/s What is the speed in km/s, km/h? a) 1000 m = 1 km = 0.025 km/s

25/1000 km/sec or

25x10-3 km/sec

b) 3600 s = 1 hour 1m = (1/1000)km 25 x 10-3 x 3600km/hr = 90km/h 5/21/2014


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Ch 2 #12

-

d

+ x

v0 = 30 m/s v = 18 m/s t = 4 sec What is the average acceleration?

a = (18 – 30)/4

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= -3 m/s/s = -3 m/s2


54

Ch 2 #14

-

d

v0 = 5 m/s a = 1.2 m/s2 What is the final velocity? What distance is covered?

+ x t = 2 sec

a) v = v0 +at = 7.4 m/s b) 5/21/2014

d = v0t + ½ at2 = 12.4 m Physics 214 Summer2014

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Ch 2 #16

-

d

v0 = 9.0 m/s a = -1.5 m/s2 What is the final velocity? What distance is traveled?

+ x t = 2 sec

a) v = v0 + at = 6 m/s b) d = v0t + ½ at2 = 15 m 5/21/2014


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Ch 2 CP4

-

d

+ x

v0 = 14 m/s a = 2 m/s2 v = 24m/s What is the time? What is the distance? Computed at 1 second intervals.? a) v = v0 + at

t = 5s

b) d = v0t + ½ at2 c) 1 sec = 15 5/21/2014

= 95m

2 sec = 32

3 sec = 51 m


4 sec = 72 57

Physics 214 Physics of everyday phenomena

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