Christmas Physics

Some people go over board with decorations. It seems all the electricity being used would start a fire. However, this year Hallmark is responsible for the danger. The following is an article found on http://www.reuters.com/oddlyenough

Jumbo Snowglobes + Sunlight = Consumer Hazard

WASHINGTON (Reuters) - 

Some 7,000 jumbo-sized snow globes were reca

lled by Hallmark Cards Inc. because the holiday decorations can act as a magnifying glass when exposed to sunlight and ignite nearby combustible materials, the U.S. Consumer Product Safety Commission said on Tuesday.

The snowman-shaped snow globes were sold in October and November at Hallmark Gold Crown stores nationwide for about $100 each.

The consumer agency said Hallmark has received two reports of the snow globes igniting nearby materials but no injuries have been reported.

Consumers who bought the snow globes, which measure 11 by 12 by 17 inches (28 by 30 by 43cm), should immediately remove them from exposure to sunlight and return to a Hallmark Gold Crown store for a full refund. 

Details about the recall were posted at the government agency's web site at: (the link didn't work, go figure)

The Color of Light

I saw a great demonstration the other day in class about the color of light. It is similar to a lesson plan found at: http://science.hq.nasa.gov/kids/imagers/teachersite/UL1.htm

To begin, my classmates drew two venn diagrams. One had the colors of paint (red, yellow, and blue) and the other had the colors of light (red, green, and blue). We guessed which colors created which new colors (orange, green, purple and yellow, cyan, and magenta, respectively).

Next, they turned on three light bulbs (a red, green, and blue one). All other sources of light was covered and a large white projection screen was against one wall. One classmate put a meter stick in the way of the light and in front of the screen. It was amazing to see the meter stick separated the light into yellow, cyan, and magenta. Then the light bulbs were turned off one at a time. When the red light bulb was turned off, the background of the screen was cyan, while green and blue were separated by the meter stick. Similar results occurred when the green and blue light bulbs were turned off. 

It was just amazing!! Try it at home if you don't believe it :o)

Vacation Science #2

I posted a slide show with a few of the pictures I'd consider for the vacation science wall...I'll add more once I get the cds with pictures from Europe out!

Careful, don't fall off the Earth!!

In class the other day we calculated the minimum acceleration we need to stay on the earth...what we found was fascinating!

First, we need to discover the diameter of the Earth as well as the time, in seconds, it takes the Earth to rotate once:

d=2*pi*radius=2*pi*6.3781 x 10^6

d=4.007 x 10^7 m

t=24hrs=1440min=8.64 x 10^4 sec

Now we have a change in displacement and time to calculate velocity:

v=(distance)/(time)=(4.007 x 10^7 m)/(8.64 x 10^4 sec)

v=463.77 m/s

We know the acceleration in circular motion is a=(v^2)/r, so plugging in the velocity and radius will give us the minimum acceleration of one point on the Earth without anything flying off!

v^2=2.1508 x 10^5 m^2/s^2

a=(v^2)/r=(2.1508 x 10^5)/(6.3781 x 10^6)

a=0.0337 m/s^2

So, we can see the minimum acceleration needed for us to stay on the Earth's surface is much smaller than the 9.81 m/s^2 acceleration we experience every day. This is the exact reason why we are able to fall down.

Imagine if the centripetal acceleration were only .0337! We would merely hover over the surface of the earth -- how crazy!?

Physics Jokes: Chickens

Why did the chicken cross the road?

Isaac Newton: Chickens at rest stay at rest. Chickens in motion cross roads.

Albert Einstein: It depends on your frame of reference, how do you know the road is not crossing the chicken?

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

There is this farmer who is having problems with his chickens. All of the sudden, they are all getting very sick and he doesn't know what is wrong with them. After trying all conventional means, he calls a biologist, a chemist, and a physicist to see if they can figure out what is wrong. So the biologist looks at the chickens, examines them a bit, and says he has no clue what could be wrong with them. Then the chemist takes some tests and makes some measurements, but he can't come to any conclusions either. So the physicist tries. He stands there and looks at the chickens for a long time without touching them or anything. Then all of the sudden he starts scribbling away in a notebook. Finally, after several gruesome calculations, he exclaims, 'I've got it! But it only works for spherical chickens in a vacuum.'

Student Teaching Ideas

At this point, my two choices for middle school student teaching is Isaac Newton MS and Mott Hall II MS both in Manhattan.

Not sure about High School...I'd still like to observe at LaGuardia HS for Performing Arts!

Why Raindrops Don't Kill Us...

I'd never really pondered the idea that raindrops might be a cause of death until the other day.

If we're concerned about killer pennies from the top of the Empire State Building, how much more scary are little water bombs from thousands of feet in the sky?

No need to fear...physics is here!!!

Since raindrops are relatively small in volume, the reach a small terminal velocity quickly. An explanation follows:

When raindrops fall, they are met with air resistance. Air resistance is proportional to surface area, so small and big raindrops experience the same phenomenon. The air continues to resist the raindrop until air resistance reaches the same value as the gravitational force. This moment is when the raindrop reaches its "terminal velocity". It can't go any faster because it's no longer accelerating. 

And since rain drops have little mass, they won't have a very large velocity!!

Good thing there's air resistance between the clouds and the ground!

Physics of Race Cars

In my Concepts in Physics course the other day at TC, we discusses race cars on a banked turn. We used free body diagrams (FBD) to illustrate where the centripetal force (the force that keeps the race car traveling in a circle).

Here is the basic FBD for a car on a banked turn. The dot in the middle of the rectangle (car) represents the car's motion out of the page and toward the drawer or looker.

So, we've got the car on the incline. The force of gravity is always directly down -- in the direction of a free hanging plumb line. The normal force (typically the force opposite the gravitational force) is always perpendicular to the surface, so not vertical in this case.

Now things start to get fun!!!!

We draw the components of the normal force in with dotted lines; pretty much, we're making the normal force the hypoten

use of a triangle. You can clearly see the vertical leg of the triangle is equal and opposite to the gravitational force.

Left over is the little bit of horizontal normal force. Notice that it is pointing towards the center of the circle...it seeks the center. The definition for centripetal force is "center seeking", so this must be the centripetal force on the car!!!!

The neat thing is, the faster the car travels around the bank, the higher it will go on the incline. The higher on the incline, the greater centripetal force. And the driver doesn't have to do a thing! All these things happen naturally :o)

I thought this was a great demonstration to show students where this mysterious and confusing force comes from. It certainly isn't magic!!!

Physics In The White House

I just read this article that President-Elect Obama has named Physicist Steven Chu as head of energy -- yay Physics!! This would be a great current event for students in the classroom to see how physics effects their every day lives. :o)

Link to Article

Centripetal Acceleration Proof

I took notes on this proof the other day while observing Mr. Provo and Mr. DePalma team teach:

Start with a circle with the velocities pointing in the tangential direction to the circle. Draw the radius so students can see the velocity is perpendicular to the radius. Label the angles and radius so students can see they are the same (even if one angle is larger, it means the arc covered in that time is longer).

The next step in the proof is some vector addition. Placing two vectors together (not using the initial vector since it has no vertical component), students can find the direction and magnitude of the acceleration. According to the image below, the acceleration will be toward the center of the circle.

This triangle (when drawn well) will be a similar triangle to those in the circle. This means we can create a ratio.

The arc(ab) can be written as the velocity multiplied by the change in time - the circle image. Therefore, the first part of the ratio can be written as v*(delta)t/r. The triangle diagram shows the change in velocity divided by the magnitude of the velocity is analogous to the first part.

v*(delta)t/r ~ (delta)v/v

Now we want to get the deltas on the same side.

(v^2)/r ~ (delta)v/(delta)t

And we know that (delta)v/(delta)t is also equal to acceleration. So...

(v^2)/r ~ a

But, this is only an approximation, so we've got to figure out how to make it exact. Well, as the angle between the vectors approaches zero (again referring to the circle diagram), the arc(ab) approaches a straight line. And as the change in time approaches zero (as measurements become more instantaneous), the velocity becomes perpendicular to the acceleration. This means the approximation we made can be exact - both the velocity and radius are perpendicular to the acceleration.

(v^2)/r = a !!!

This isn't the most clearly written proof, but I'll work on it.

Things to remember:

- As velocity increases, so does acceleration.

- As the radius increases, the acceleration decreases.

Book Recommendation: 5 Easy Lessons

I was observing at Brooklyn Tech High School yesterday and a teacher (Mr. DePalma) recommended the following book:

Five Easy Lessons by Randall Knight

Five Easy Lessions: Strategies for Successful Physics Teaching

• "An invaluable resource for any instructor interested in creating a physics class where students are actively engaged in learning and applying physics. The book is filled with specific suggestions on teaching individual topics in addition to an excellent summary and overview of teaching strategies based on physics education research." — Michael Read, College of the Siskiyous, CA
• "One of the most complete and helpful books on teaching introductory physics that I have ever come across. Not only does it provide thoughtful suggestions about how to improve your course topic by topic, it provides a marvelous primer on educational research into how students learn (or fail to learn) physics." — Dale Pleticha, Gordon College, MA
• "I have used the great ideas from this book over the last few years. It contains excellent summaries of research into students' learning and offers lots of helpful and specific advice on how to bring the ideas that have emerged from this research into your classroom. It is a valuable resource for improving students' learning." — Larry Lonney, Shawnee State University, Portsmouth, OH

Phase Change Graph

As you may have experienced yourself, creating graphics in Microsoft Word is a huge pain! However, I've created this phase change graph for the phase changes of water. Enjoy!

Excellent Physical Science Book

I was given the Teacher's Edition of this book as a graduation present and it is EXCELLENT!!

The diagrams are really useful and there are many types of assessment questions at the end of every chapter. It has a wide range of Physical Science topics that are very approachable for students.

If you get the chance, check it out!

An Introduction to Physical Science by Shipman, Wilson, Todd.

What Engineers Do When They Retire...

Teacher Resource Websites: Evolution and AMNH

Here are two websites that would be useful for teachers:

Berkley's Understanding Evolution

American Museum of Natural History Educational Resources

Science Blogs!!!

Just found this blog for Science and Math teachers which focuses on free resources!!!

Check it out:

SCIENCE, MATH, AND TECHNOLOGY BLOG

Another blog is for parents and caregivers: 

BRIGHTEST KIDZ BLOG

Vocabulary Pictures

I was chatting with my cousin at a family gathering today and asking her questions about the Physics class she's currently taking (she's a 9th grade student). She mentioned on homework assignment that got me all excited!!!

As a test is approaching, the teacher gives each student a list of vocabulary words. The students are responsible to "surf the net" and find pictures they can use to illustrate each word. The same picture can be used for each word, as long as the student can skillfully explain the connection. 

I think this is a great way to get kids thinking about Physics in their everyday lives and a creative way to get them out of the textbook!!

Never mind the fact that it is a useful assessment tool for teachers. I'm sure this teacher can easily tailor his exam reviews based on the kids' assignment answers!!

Citigroup is Falling Down

No, I don't mean the company is falling apart due to the economic crisis of 2008...

I read recently in the book Einstein's Refrigerator, a story about the Citigroup Center building in Manhattan (the building pictured to the right with a triangular roof). The book, compiled by Steve Silverman, is a collection of believe-it-or-not stories "from the flip side of history."

In the Citigroup story, a college student from New Jersey calls the engineering firm responsible for the building, claiming a flaw in the design poses a much larger threat than anyone realizes. Out of curiousity, the chief structural engineer William LeMessurier looks at the plans and does some quick math. He finds that the design leaves the building at a 40% increase in stress if hit by a quarterly wind. However, he learns the on-site engineer decided to bolt the structure together instead of welding (as the plans dictated) and t

he math under that circumstance showed an increase in stress by 160%!!!

The other problem was the fact that one corner of the building hung over St. Peter's Lutheran Church. You can just barely see the church in the left bottom corner of the picture at the rig

ht.

To make a long story short, Citigroup wanted to keep this huge error in engineering on the "down low", so all the work done to fix this problem was done in the middle of the night. No one ever knew the building was being fixed and strengthened while they were sleeping!

No one knew, but people wondered why there was a glow near the Citigroup building every evening. LeMessurier even got a call from the New York Times at one point. Lucky for him, they went on strike that very evening!

So, needless to say, the Citigroup building is safe now. If it had ever fallen over, the Red Cross estimated it would have caused 156 city blocks worth of damage! That's almost the whole of Manhattan!!

I share this story, because it is a great way to use current events to teach Physics! The main issue of this problem is the building's center of mass and more specifically loads and torques. Students might enjoy doing the calculations LeMessurier did and determine the safety of the building themselves. Below is a quick description of the building.

Great Website: Engineer Your Life

My mom recently showed me the website below. So cool! I'm just disappointed the website doesn't have any teacher resources...but it's great nonetheless!







Check it out ---> http://www.engineeryourlife.com

Evolution Activity

So I observed David McKinney, an 8th Grade Science teacher at Isaac Newton Middle School, today. It was really exciting to see all his energy -- even if he admitted part of his energy high was due to having observers in the room! He did the following activity with his class and it was so fun to watch, never mind that the kids could see evolution (a change in frequency of a species) in action.

Based on Sir Charles Darwin's research in the Galapagos Islands, the kids were challenged to see which finch beaks (modeled with tweezers, clothespins, toothpicks, and spoons) were most effective in eating which foods (rice, sunflower seeds, marshmallows, and marbles). At first, the kids had a plate representing an island since Darwin found there were entirely different species of finches on the islands in comparison to the mainland. Each student made a prediction as to which "beak" would be the most effective. Then they emptied a bag of food onto the plates (each bag had an assortment of the "foods" listed above). They were given 10 seconds with each "beak" to see how many pieces of food they could collect in a cup: NO SCOOPING WITH THE CUP ALLOWED! Results were recorded in a chart and organized by the type of food.

The second half of the activity was based on the first. Half of the groups were given a bag of rice and the other half a bag of marbles since their respective islands had a drought of the other food. Kids predicted which beak would be most effective in this case. Each beak had 10 seconds to prove itself and the data was recorded.

McKinney ran out of time at the end of class, but they had a short discussion about why certain beaks were advantageous given the indigenous food supply. It seemed empowering for the kids to participate in an experimental activity similar to the acclaimed scientist Darwin that it is associated with!

**I later found out this activity is a state mandated lab activity for the Regents. Another variation we did in class was to have students sift "food" through a paper plate with holes in it.

Atomic Humor

Two atoms were walking across a road when one of them said, "I think I lost an electron!" "Really!" the other replied, "Are you sure?" "Yes, I 'm absolutely positive!"

Pendulum Conundrum

A classmate and I were mulling over pendulums on the train ride last night and couldn't come to any conclusion. We were discussing how mass as a variable effects two pendulums. Initially, my response was that a more massive pendulum would rise to a higher point once released (if two pendulums of differing masses were released from the same height) because it has greater PE, but then we got confused because it also takes more energy to keep it swinging. So then it also made sense for both pendulums to reach the same height and have the same period with every oscillation.

Since we couldn't come to any conclusion, I went home and played around with some homemade pendulums. I constructed one with some gift wrapping ribbon and one fork and another with gift ribbon and five forks. Attached is a slide show and commentary of what I found. I pretty much observed both phenomena of the two forks at same heights with same periods as well as two forks with same periods but different heights. Then I coupled the two pendulums just for kicks.

My husband Keith got home from work as I was curled up nearly under the sink in the bathroom trying to take pictures. Oh, Physics!

Bringing Vacation Science to the Classroom

I've been thinking about how to decorate my classroom...I've had tons of ideas run through my mind, but one has stuck. I want to create a wall of pictures of places I've been related to science (or just cool places I've been!!!). Eventually, students and other teachers could add their pictures and we'd have a whole story board of science around the world! Here are some of my vacation ideas:

PLACES I'VE BEEN
CERN -- the world's largest particle accelerator in Geneva, Switzerland, June 2007
Kennedy Space Center -- NASA base in Cape Canaveral, FL, June 2005
London Eye -- large ferris-wheel type attraction ran on hydraulic power, March and April 2007
Mt. Washington -- super awesome mountain to be hiked and conquered! July 2006

Niagara Falls -- source of power and amazement, April 2008

PLACES I'D LIKE TO GO

Hoover Dam

OTHER PLACES OF INTEREST

Empire State Building, NYC

CitiGroup Building, NYC

Brooklyn Bridge, NYC

Cool Bridge in Boston, MA

Washington Monument, D.C.

Tallest Building, Dubai U.A.E.

Units and Books

I was thinking the other day about how I could possibly create bigger units for the year to add some current events to my class and make it applicable to my students. One thought is to have a Space unit, which could cover mechanics and electricity & magnetism. I still need to think of a unit to cover waves, modern physics, and whatever other material I might want to cover.

The idea of literacy is central to the Teachers College ideology, so I have been looking out for ways in which to implement that in my future classroom. A usual favorite is current events picked by myself and/or my students. Another option (adapted from Sephali Ray at Patrick Henry Middle School, NYC) would be to have students read science fiction. I would assign a middle school level book for my high school physics students and use book discussions to stimulate thinking about scientific ethical issues. Hopefully it would lead towards some scientific literacy!!

The Start To A Long Journey!!!

I'm just using this blog to keep track of my thoughts while I am preparing to become a science teacher. In the future I hope to use it to journal my experience as a first year teacher and beyond!