Monday September 28

We started out today in class going over vector addition. We discussed how vectors represent two quantities, force (or velocity, acceleration, or displacement) and direction. Then we continued working on our vector packet. We sketched and then added the vectors of two spring units pulling a block as illustrated below.

This is the arrangement of the block and the springs. The springs are the gray lines.

This is an illustration of using the tail to tip method of adding vectors. The two gray lines represent the springs and the blue line represents the actual force exerted on the object.

Then, we took a washer and three spring scales and pulled on the washer with all three spring scales so that it wasn't moving. Then, using a giant circle with degree measurements on it and the reading on the spring scales, we found the force and direction that each of the spring scales applied to the washer. We graphed and then added these as vectors, which should have looked something like this.

Our Homework was worksheet 3F, which had 2 pages. The next scribe is Rahul.

useful tutorial on vector addition

If you're a bit unsure about what we did today with adding the three forces on the washer, you might want to take five minutes to follow along with this quick step-by-step tutorial.

Adding vectors graphically

You can find many more tutorials by googling "graphical vector addition", and even some interactive demos by googling "graphical vector addition applet."

Newton and Newton's 3rd Law

Here's a fascinating letter from The Physics Teacher (A very cool magazine, if I do say so myself), about Newton's own discovery of the idea of forces coming in equal and opposite pairs. I've bolded the most important part

NEWTON AND NEWTON’S THIRD LAW
Just as students have difficulty with Newton’s third law as discussed in the article by Lehavi and Galili, it is of interest to realize that Newton’s under- standing of the significance of the mutual interaction of bodies in their motion did not occur until very late leading up to his writing of the Principia. Cohen published an article on this, which also appeared as an appendix in a revised and updated version of his book.

Newton wrote an essay entitled “De motu” in which he described a calculation of the orbit of a planet in our solar system. He ran into the problem that his calculation did not fit the actual data sufficiently. He realized that assuming a stationary Sun was a potential source of error. He recalculated, but this time he allowed the Sun to move in response to the pull of the planet. The revised calculation yielded numbers within the error of measurements of the orbits of the planet available at the time. Apparently, the notion of the third law of motion was not an explicit and automatic part of Newton’s thinking until this point.

According to Cohen this work was completed shortly before Halley’s visit with Newton, which led to the writing and publication of the Principia. This is in distinct contrast to the impression one often gets from descriptions of Newton’s life in physics textbooks that he went home to avoid the plague dur- ing college and in two years worked out all of his contributions to physics. We should know better and do better in our textbooks because serious historical scholarship on Newton is now eas- ily accessible.

The final paragraph in the article by Lehavi and Galili illustrates the magnitude of the problem caused in physics education by the emphasis in texts on presenting as much of the canon of physics as possible. At best students develop a kind of technician’s view of physics, which is that the goal of learn- ing physics is to remember a list of calculations and facts. In doing so students miss the essence of physics, which is the construction of4 explanations of physical phenomena. Is it any wonder then that students yearning for such intellectual challenge choose other fields to go into?

Dewey Dykstra
Boise State University

Friday, September 25

Today in class Mr. Burk gave us back our Homework 3d. We then went into a long discussion about the Inertial Balance vs. Regular Mass Balance. The inertial balance is what is used in space to measure weight, because everything is moving in a constant free fall, so there is not enough gravity to be able to measure. In the end the measures of each kind of mass end up being the same.

After we discussed the two types of balances, everyone went to the lab table and we discussed the free body diagram of a horse pulling the wagon. "According to the horse", he should not be able to move the wagon because every force he puts on the wagon, the wagon counteracts equally and oppositely. After much discussion, we came to the conclusion that the friction of the horse pushing against the ground gives the horse the extra leverage to actually move the wagon.

The final activity we did in class was to begin the vector lab. Mr. Burk had a contraption of two rulers screwdrived together so that one ruler went out 50 cm or 1 spring unit before the other ruler crossed it perpendicularly. First we did a control test of 1 spring unit, and then wrote predictions for the two spring units. Most everyone said it would be exactly double even though the springs go out at angles and are not pulling straight in front of the cart. It ended up that the two spring units on the ruler contraption only pulled the cart with an acceleration 0.7 m/s/s faster than one spring unit, which was not close to double. We then tried to figure this out, and did not finish the discussion, but so far it looks as though it involves finding the leg of the 45 45 90 triangle and doubling it to find the amount of force.

Homework: Finish the Inertial Balance lab and Homework 3E

Next scribe is Paxton.

On the subject of bottled water

Hi All,
on friday we had a semi-serious discussion about the evils of bottled water. Here's a link to the article I mentioned discussing some of the problems and environmental harms of the bottled water industry.

Message in a bottle

Some crazy facts:

• Americans spent more money last year on bottled water than on ipods or movie tickets: $15 Billion.
  
• We pitch into landfills 38 billion water bottles a year -- in excess of $1 billion worth of plastic.
  
• We're moving 1 billion bottles of water around a week in ships, trains, and trucks in the United States alone. That's a weekly convoy equivalent to 37,800 18-wheelers delivering water. (Water weighs 81/3 pounds a gallon. It's so heavy you can't fill an 18-wheeler with bottled water--you have to leave empty space.)
  
• And in Fiji, a state-of-the-art factory spins out more than a million bottles a day of the hippest bottled water on the U.S. market today, while more than half the people in Fiji do not have safe, reliable drinking water.
  
• If the water we use at home cost what even cheap bottled water costs, our monthly water bills would run $9,000.
  
• Half the wholesale cost of Fiji Water is transportation--which is to say, it costs as much to ship Fiji Water across the oceans and truck it to warehouses in the United States than it does to extract the water and bottle it.
  
• Sometime this year, Fiji Water will eclipse sugarcane as the number-one export from Fiji. That is, the amount of sugar harvested and processed for export by some 40,000 seasonal sugar workers will equal in dollar value the amount of water bottled and shipped by 200 water bottlers.
  
• Worldwide, 1 billion people have no reliable source of drinking water; 3,000 children a day die from diseases caught from tainted water.
  

Anyway, if you read this and still think "bottled water tastes better" let me know, and I'll be happy to set up a test to show you that you can't distinguish bottled water from the water right out of the tap in Westminster, or your house for that matter.

Difficulty with the Lab

Hey, I'm not sure if anyone else is experiencing this problem but with Part 3 of our lab I really cannot come up with a way of finding the mass of the clamp. I know we did something with 6 clamps and 200 grams and I have data for that but I do not think my formulas are correct. Can anyone help me?

Class on Wednesday

Class On Wednesday

At the start of class Mr. Burk handed us back our reassessments that we had taken. The two reassessments that we got back were one that was about Concepts 2.3, 2.3(again), 2.5.2, 2.3.3, 2.5.2(again). In this reassessment it went over a position vs. time graph and how to read it. Also we had to explain it and write an equation, and tell the instantaneous velocity of the cyclist by using the tangent slope method. The other paper that everyone got back was a paper that was about acceleration vs force graphs and also 1/a vs mass graphs. We had to find out the frictional force and how mass afects the acceleration. 1/a vs mass is proportional which is pretty much the same thing as saying that acceleration is inversely proportional to mass. That being said if Mass doubles then acceleration will do what? It will be cut in half. The last thing we got back was 3C in which we went over forces that included vectors in them and the magnitude of them. Also we had to find out the tension forces of strings with weights hanging from them. Then we had to sketch position vs time graphs, velocity vs time graphs, or acceleration vs times graph; for a certain set of data. After the first five minutes of class we went over 3D in detail and made sure that everyone understood that homework assignment. We briefly went over what our homework was and that it was to have the Inertial Balance Lab done by Friday (which is our next class period) and we had to have four parts to it. The three parts include: amplitude independence of inertial balance, determining the relationship between period and mass, massing a clamp in grams, and understanding a complex system. The amplitude independence of inertial balance we have to write a paragraph to show that we understand how the amplitude did not affect the period of the inertial balance. For determining the relationship between period and mass we have to make a period vs mass graph , find a linearized version of that graph and then write an equation for the linearized graph and include a paragraph along with it, then we must write one paragraph and make a graph theat explains how to find out the mass of a single clamp in grams. For understanding a complex system we must understand that if you add mass to the balance or suspended from it it doesn't change the results. Use this to explain why we draw free body diagrams of complex things as simple dots. Finally, for the last thing that we did during this class period we took notes on some new topics:

How does the tension force of William on Sana

compare to the tension force of Sana on William. (They are equal in size, opposite in direction)

A novice student would say that the stronger person pulls harder, when in fact this is wrong. An observation that we made in class is that when two people pull on each other's spring scales, the force reading is the same. Also, the force acting on person 1's spring scale is done by person 2. And the tension force acting on person 2's spring scale is done by person 1. This class covered some interesting concepts and a really big idea that had previously been discussed that when the Force(net) is = 0, the velocity is constant. Whether it is not moving or just moving at the same speed it was moving. The scribe for Friday... is Burge.

A great bio in the NYT, and some AWESOME pics

The NYT has a wonderful feature on Carolyn Porco, head of camera team of
the Cassini space probe which was launched to study Saturn.



You've got to see some of the images (click on the image to see at full resolution):

How to submit assignments electronically

A few of you have been emailing me assignments, and while this as been great, I'm realizing that keeping track of these assignments is difficult, given the number of emails I am getting, so I'm setting up this process for submitting work. If you plan to submit an assignment via email (and I encourage you to do so, I ask you follow these guidelines:

1. Submit a readable document (I can read all versions of word, open office, pages, excel, etc). If you write your stuff in something crazy like wordperfect 1.0, email beforehand to make sure I can read it. If I can't open the document, YOUR GRADE IS ZERO, AND WILL REMAIN THAT UNTIL YOU SUBMIT A READABLE ASSIGNMENT (AND YOU WILL SUFFER A LATE PENALTY).
   
   
2. Follow the following convention for naming your document:
   "Period number Last Name First Initial Assignment title. " So Bob Smith, submitting his texting paper from 7th period would title his document: "7 Smith B Texting Letter" without the quotes. Do not name the assignment unrecognizable things like "texting paper" or "stupid physics assignment." (you might lose points for the second one).
   
   
3. If you got an extension from me in advance, please copy and paste my response to your request into the body of your email to me.
   
   
4. Follow the same convention for your subject line that you do for naming the document. "7 Smith B Texting Letter."
   
   
5. Email your attachment, FROM YOUR WMS Account (or otherwise easily recognizable email, not laxgirl17@aol.com) to the following addresses (add these addresses to your address book):
   
   For 1st period: jburkWMS+1stper@gmail.com
   
   For 3rd period: jburkWMS+3rdper@gmail.com
   
   For 7th period jburkWMS+7thper@gmail.com
   
   

Thank you in advance for following this procedure. It will greatly simplify my record keeping, and will allow me to return assignments to you more quickly. AS a reward for submitting your assignments following this procedure, I will give +1 point bonus for all assignments submitted using these procedures (you can resubmit if you've already submitted). In the future, I might deduct points for submitted assignments that do not follow this procedure.

Friday's class

On Friday, we started class by taking notes, and trying to write formulas for constant velocity and acceleration graphs. This was a good exercise that showed us that we do not know as much as we think we know. After that, we took notes involving the formula for constant acceleration and a more in depth analysis of newton's 2nd law. After the 1st half of class ended, we then started thinking more about the relation of mass to motion by doing a lab that showed us that the more mass there is, the less velocity there is .(I was not in the room for the explanation, so do not quote me on this) We did this by using a flimsey piece of metal and measuring its velocity w/ a motion detector. We learned that when we added mass, the velocity was lower than w/o extra mass.

Wednesday, Sept 16

Wednesday in class we learned how the bass unit for a kilogram is always changing. We learned that the units of electricity and many other things are greatly affected by this always changing golf ball shaped unit of mass.

We also learned how important it was for humans to be able to use and read graphs. We used shopping at a grocery store as an example. We solved which line would be the fastest to go through by making a graph and then interpreting it. We then watched a video on a great math teacher demonstrating this method on the news. It was shown that going to a line with two people with ten items each would be about 5 minutes faster than going to a line with seven people and 1 item each. After solving for this information we took an ungraded assessment to see what we knew and could understand on the subject of reading graphs.

the next scribe is dylan

How to blog

I finally had a spare moment to put together a short jing on how to blog, and a couple of other neat features of the website. Check them out here:

How to blog (< 2min)

How to put an equation in a blog post (< 2 min)

How to search the blog and use the class calendar (< 2min)

The kilogram

Here's the link to the wikipedia entry for the kilogram. There's a lot of info here, some of which you won't understand, but a lot of which you will. And it should fascinate you to know that there still is so much work going on to define something as seemingly simple as a standard of mass.

Here's a story about the kilogram losing mass.

Who knows, maybe you will grow up to be the scientist who develops the most precise mass standard for the kilogram. That would be one major way to change the world.

Tuesday's Class

The first thing we did in class today was take a reassessment on position vs. time graphs. Then, we started to analyze the graphs we made for homework. We determined that force and acceleration is directly proportional and that mass and acceleration were inversely proportional. Then we somehow figured out that a=f/m. We decided that this was Newton's 2nd Law. Then we had free time to work on homework or think of ways to convert spring units to newtons. That's all we did today in class. Tomorrow's scribe is Gaston!

Class on Monday

The class on Monday started with receiving our grades. We discussed how the grades are not accurate because we have not reassessed every concept yet and their have only been a few grades. Also, Mr. Burk said that he did not send out any comments for our class. YES! Then we moved on to interpreting the acceleration vs force graph for the spring cart lab. We discussed why at a=0 cm/s^2, f=0.3 su, and came to the conclusion that it is the contact frictional force of the table on the cart. We then tested in a lab how mass affects acceleration by keeping the number of springs constant but changing the number of bricks on the cart.
The next scribe is Alexis!

More gold from study hacks

I've already told you exactly what you need to do to ace physics (go back and read my post about how to study for a physics assessment. But maybe acing physics isn't enough for you. Maybe you want to ace all your classes, become deeply intellectually engaged by what you're learning, and change the world. Well, Study Hacks strikes again, with a great post titled "The Definitive Guide to Acing your Schedule." The post is again more aimed at college students, but easily adapted to high school, and the advice is pure gold.

Setup a separate chat with your professor, your TA, and a student who took the same course in a previous semester.
In each chat session, ask the same question:
If you were to write an advice guide about doing incredibly well in this class, what would the chapters be?


It takes around an hour to complete this exercise. But it’s results are near magical. Gone is the guesswork about notetaking, reading, and how best to review. In its place is specific advice that is tuned to the specific challenge you face. You’d have to be a real slacker not to do well with this treasure map in hand.

Ok, so you don't have a TA, but imagine if you set up a meeting during backwork with one of your teachers and you asked him/her this question. What would you learn? You might also help your teacher to think carefully about what is necessary to ace a class.

Class on Wednesday

In class Wednesday we went over a lot of new material with forces. One of the main concepts was that in the absence of forces an object moves with a constant velocity, that was one of the things we were all supposed to understand after that class period. We started off going over that the general wasy to describe forces is that forces require something to exert the force on and something that exerts the force. From now on, we will be describing a force as, The force of something on something. We also learned how to describe such a generic term such as gravity, the non-contact gravitational force of the earth on the block. Then we went over a system schema, how to draw them and what forces and objects they should include. The free body diagram was another diagram that we learned how to incorporate with forces, and the slope of the rays from the dot if the surface is sloped. Also instead of writing out the non-contact gravitational force of the earth on the block every single time we learned that you can do this, Fg, E-->B and that is telling the exact same thing. The class on wednesday covered a lot of material, and all of it was very interesting. The next scribe is... Joe for the class on Friday which we already had.

September 10, 2009

The first thing we did in class today was take a reassessment over graphs of motion. Then Mr. Burk showed us a picture of a green blob in the air, which we determined was a tennis ball falling. We determined that the tennis ball was moving because it was blurred, and because one side of the blob was more translucent than the other, we determined that the tennis ball was accelerating. We used the shutter time, the diameter of tennis balls and the constant acceleration caused by earth's gravitational pull to calculate the average velocity of the tennis ball. For this, we used the equation , finding the change of x by measuring the start and end of the green blob, finding the difference and then subtracting the diameter of a tennis ball from that. Then we made a velocity vs. time graph and found the area under the graph to discover the height from which the tennis ball was dropped. After that we were done analyzing the picture of the tennis ball, so we started on a lab. The goal of the lab was to find the relationship between force and acceleration. We did this by pulling a cart along a table and measuring the force acting on it and the carts acceleration. We measured the force acting on the cart by pulling the cart with a set number of springs, because each spring, stretched to a constant distance, exerts a constant force on an object. We measured the acceleration of the object using the motion sensors. Finally, we graphed the force on the cart verse the acceleration that the cart was experiencing and found that they were directly proportional to each other, when friction was taken into account. Our homework was worksheet 3B. The next scribe is Matthew, unless he has already gone. I'm not sure.

Great new album from they might be giants

Hi All,
As I mentioned in class, They Might be Giants released a great new album filled with fun songs about science this week. They've also put up a video of the first song from the album, "Science is Real." Check it out...

Humorous idea for the day

Luckily, in this class pain doesn't have to be your teacher.

September 8, 2009

Yesterday in class, we had a long discussion on the history of grades. We went back in time, imagining what the grading system would be like as our civilization developed, and came to the realization that our grade system is there simply because it is the easiest one to use, but the least effective at encouraging improvement and understanding.

We received our tests back, and were told not to worry about what grade you get. Be happy for a three, and especially a four if you had two back to back threes. In general our class topped both a junior and sophmore class that took the same test, so we all did really well.

For our lab of the day, we used tracker to see the movment of Adrian Wilson jumping over a 66 inch bar. By analyzing the points of his head from his peak to the bottom, we found his acceleration was -9.8 m/s, which proves that gravity was pulling him down. We also started on proving that the gravity on the moon landing was different, but not everyone finished.

HW: Play around with and get to know tracker. Prove the moon landing was real if you haven't already.

I don't know who hasn't gone yet so just volunteer in class.

Are you living well or preparing to live well?

Another great post from study hacks. Here's a quote:

The happiest students are those who try to shape their life into something that’s meaningful, quality, and enjoyable right now; the type who get excited about the philosophy seminar they got into, and then spend an early Fall day outside getting acquainted with the reading. These students aren’t afraid of hard work, but they keep it carefully contained, because they know there’s a lifetime more where that came from, and if they can’t handle it well now, when will they ever?



If you’re not trying to live well now, what are you waiting for?

Remember, I'm always free during backwork (or just about any other time) to talk to you about how to put these ideas into action.

Definitely worth 20 minutes of your time

No matter what your politics are, you should take 20 minutes to watch this speech by the president today about how hard work and goal setting can help you to achieve your dreams, and solve the world's problems. It's wonderful speech worth serious thought.

Tracker Lab Stuff

Our next lab is focused on determining if the moon landings were hoaxed.

Here are some tools you will need:

Tracker Video Analysis: A great piece of software for analyzing motion recorded in film clips

Tracker tutorial video: A nice video that explains what can be done with Tracker.

Here are links to the the videos we will analyze on youtube. You should actually use the copies of these videos stored in V:\Burk\Honors Physics\Tracker Lab.

66 inch jump: this guy gets some major hangtime, jumping a hurdle taller than himself.

Apollo 16 crew salutes the flag: 'Supposedly' shot on the moon, your job is to find out if this motion is any different than our high jumper's.

Friday's class

On Friday we spent half our time reviewing for the assessment by looking over the review packet, and also answering any other questions about the assessment and the material. Our review consisted mostly of packet questions, including a bullet analogy, but we also had some other motion questions. Overall, from the review we learned that graphs are our friends!

After the review it was test time! I am not sure weather I can talk about the test online, so I will play it safe and not mention the actual content except for the cartoon on the front and the work checking guidelines. Both of these resources were very helpful during the test.

Friday was overall a good class. Next scribe is....................................BURGE!!!

Review for Chapter 2 Test. Question.

I'm having trouble with that problem about the two balls traveling down a track. It's a ball so I guess that means rolling friction means friction isn't a big factor, but they seem to have the same amount of plusses and minuses for the velocity. 1 doesn't have any and 2. increases speed then decreases to back to "original speed" which one is faster in that case. The only difference between the two is the changes in velocity. This applies to 4 and 5. Any ideas?

September 2, 2009

These are the things we did and talked about in class today:

We talked about yesterday's double class period and how successful it was. We decided that it worked well; not only was it an enjoyable (more or less) way to spend two hours, everyone learned a lot and gained a better understanding of the material that we will be assessed on this coming Friday.

Mr. Burk talked about why assessments in this class should not be stressful in the least. First of all, it is very, very difficult to score an 100 on the first try (if you show mastery of a concept, you will receive a 3 out of 4 and only receive the 4 out of 4 after showing mastery a second time). Also, if you were having a bad day and somehow just couldn't seem to show understanding of a concept on the day of the assessment, there will be numerous opportunities to improve your grade. This method of testing is effective in that you won't go far in this class or in life by just memorizing equations and doing textbook problems over and over again. You must truly understand a concept to succeed, which this method of testing attempts to measure.

Mr. Burk gave us a cartoon printout which at the end had some physics problems involving velociraptors and velociraptor food (i.e. people). We spent about 20-30 minutes working the first of the problems out on the white board. It was a fairly difficult problem that involved calculating the time it would take a velociraptor to catch a person and we needed to use two graphs to solve it, a position vs. time graph and a velocity vs. time graph. The objective was to find the point in time where the person's position was equal to the velociraptors position. This was accomplished by finding the position on the position vs. time graph where the lines representing the person and the raptor intercepted. This could also be accomplished by using the velocity vs. time graph and taking the areas under the two lines (which is equal to displacement) and finding the time where the raptor had traveled 40 meters more than the person (the person had a 40 meter head start).
*By the way, I tried to upload pictures of the work Mr. Burk showed on the white board but I couldn't transfer them into the text box.

We then went over the first page of Homework 2D. The first half wasn't very difficult; it gave you a x vs. t graph and you had to translate it onto v vs. t and a vs. t graphs. The 2nd half was more confusing, showing information on the v vs. t graph. While translating that into terms of a vs. t wasn't very hard, moving that onto the x vs. t graph was much more difficult and took very careful thinking (one of the difficulties lay in realizing that a negative slope on a v vs. t graph can still show forward motion as long as the line still lies above the origin line).

That's all we did in class today. Tomorrow's scribe is Dylan (for real this time).

I don't understand....

Hey everybody! If you could help me out by explaining things that would be super.

So on the Unit 2 Major Concepts sheet I don't understand:

-2.7

Can you find the displacement of an object moving with constant acceleration from a velocity time graph?

-2.7.2

Can you apply the model for constant acceleration (2.12) to determine the displacement of an object?

-2.8

Do you understand how our methods can be extended to deal with objects with non uniform acceleration?

Thanks so much!

Alexis

LHC Live Video Feed

This link will take you to a website where you can see a live video feed from the Large Hadron Collider.

http://lhccam.com/