A really cool demonstration of momentum and energy.  Try to understand this one!  Where can we get long bead chains like this?!?!?!  We must try this one in class.

TED: Freeman Hrabowski and his 4 Pillars of College Success

A talk from the President of University of Maryland, Baltimore.  He marched with Dr. Martin Luther King as a boy, and now works on getting minorities, the poor, and other underrepresented groups into science and math.

Video for an Explosive Use of Capacitors and Conservation of Momentum, Watermellon style!

Courtesy of Louis S.:

The video I chose actually represents two aspects of physics in this class.  The set-up of the watermelon explosion is simply a large bank of capacitors wired together in series with an extremely high voltage. When one of the capacitors is discharged, there is an enormous current that runs through the watermelon, causing it to explode. This shows the relationship between capacitance, voltage, and current.  The other portion of this class can be seen with the high speed camera showing the watermelon explode.  When the watermelon is initially at rest, its momentum is zero.  Then, once it explodes, all of the little pieces of watermelon-shrapnel must fly off such that the components of their motion must equal zero.

Congratulations to the Class of 2013!! You will be missed

Each year this is a bittersweet time for me.  I hate to see the senior class leave, but at the same time I am tremendously happy for and proud of the students.  You are about to enter a new phase of life, and also one of the great times in life.  You are all prepared for college on the academic side, and you will quickly learn and adapt to independence on the personal and social sides.  Enjoy the experience!

Here's to the Class of 2013!  A job very well done!!
- Doc V

Congrats on Surviving AP Season!!

AP exams are done today, so Congratulations!!!!! 

Samsung Short Essay Contest on How Technology Helps Us Learn

Samsung is sponsoring a short essay contest for high school students.  You can write and submit a 300-word essay: An essay up to 300 words on what you think about technology advancements and how it will change the way we learn in the future. Is it for the better?

This could be fun.  This is also only about a single page essay on any technology you wish to address.  Give it a try.  Five scholarships of $1000 will be given to those papers judged as being the best.  Just let me know if you have an interest, and the link above allows you to sign up for the contest. 

Possible Hints of Dark Matter

Check out current results from two experiments, that show first hints of evidence for dark matter.  This is a proposed explanation for the observed motions and structures of galaxies, which cannot be explained by the amount of observable matter astronomers measure.  It will be an exciting story to follow over the coming months and years, as more data is collected and analyzed and scrutinized by physicists.

Possible Discrepancy in the Size of a Proton - IF Real, New Physics???

New measurements of the size of a proton, using a new method of muon interactions with protons rather than electron interactions for protons, reveals a ~4% discrepancy in the proton radius between the two methods.  Physicists are trying to figure out if this is due to some mistake being made with the muon experiment, or possibly some misunderstanding of systematic uncertainties in the experiment, or other 'boring' explanations for the difference.  The story can be found here.

However, if this result and difference hold after all the investigations are completed and are statistically significant, then this could be an indication of new physics beyond the current Standard Model theory, which is the foundational theory in particle physics for the past five decades.  Time will tell as the current experiments, as well as new experiments being designed and run to check these results, are completed over the next 5-10 years.

This is a wonderful example of how science works.  Experimental results are published in peer-reviewed journals, and are scrutinized by the scientific community.  When a discrepancy comes up with well established and well tested ideas over long periods of time, one needs to seriously and open-mindedly look at all possible explanations for the discrepancy. Results must be reproducible by independent groups.  Possible new explanations must be considered and tested and debated.  It is a slow process, but the goal is to uncover the truths in Nature, if at all possible, based on physical evidence.  This makes for the excitement that scientists encounter in their research programs!

EM Induction Links We Are Using

We are first keeping a focus on examples of Faraday's law where induced emf = -B dA/dt.  This is when the wire loop or circuit is moving into or out of a region where there is a magnetic field.

1) The good news is that the math is always the same - the result is induced emf = -Blv.

2) Also, because the free, delocalized electrons of a moving conductor are actually moving, they feel a magnetic force F = qv x B...this is the force that starts the current in the wire loop!

3) Then, this induced current is in the external Bfield, and feels a force F = Il x B.  This magnetic force on the wire loop will be opposite the velocity, acting like a magnetic brake.

Check out these videos:
http://docvphysics.blogspot.com/2012/04/moving-conducting-rod-through-b-field.html
http://docvphysics.blogspot.com/2010/04/how-to-do-faradays-law-for-changing.html
http://docvphysics.blogspot.com/2012/03/how-to-find-terminal-velocity-of.html
http://docvphysics.blogspot.com/2012/04/rotating-conducting-rod-in-b-field.html

Some good simulations that show applications of EM induction.  Play with these, change parameters, and observe what the effects are of things like rate of change of flux, how the flux changes, the number of coils, DC versus AC currents, and the area of the coils.
http://phet.colorado.edu/en/simulation/generator  Click on Run Now, and see the five different simulations that can be run, including generators and transformers and pick-up coils.  Also keep Lenz's law in mind to see if Nature is trying to stop the magnetic flux from changing.

Also, this one is on Faraday's law:
http://phet.colorado.edu/en/simulation/faradays-law Click on Run Now, and move the magnet like in our labs  to create an AC current.  Pay attention to Lenz's law, and see if it makes sense with what you observe in the simulation.

The Higgs is Officially Discovered!

Watch and learn the history of physics from the ancient Greeks up to the newly discovered Higgs boson, in just 30 minutes!  One of the speakers in the video is Melissa Franklin, who I knew at Fermilab.  She is a physics professor at Harvard.