Year: 2011

Honors Physics Essentials Only $12.95!

Posted on by — No Comments ↓

Happy Holidays!

clip_image002I am thrilled to announce the release of Honors Physics Essentials, an algebra-based physics book designed to assist beginning physics students in their high school and introductory college physics courses as an invaluable supplemental resource in class as well as a review guide for standardized physics assessments such as the SAT Subject Test in Physics, PRAXIS Physics, and CST Physics exams.  You can find it online at Amazon.com for only $12.95.

Honors Physics Essentials is an easy-to-read guide to algebra-based introductory physics, featuring more than 500 worked-out problems with full solutions and covering topics such as: kinematics, dynamics, momentum, impulse, gravity, uniform circular motion, rotational kinematics, work, energy, power, electrostatics, circuits, magnetism, microelectronics, waves, sound, optics, thermal physics, fluids, and modern physics.

The 384-page 6”x9” paperback book is integrated with the APlusPhysics.com website, which includes online question and answer forums, videos, animations, and supplemental problems to help students master Honors Physics Essentials.  You can find more information at http://www.aplusphysics.com/honors.  Volume discounts and e-book versions are available, as are class and site licenses for electronic versions starting as low as $3 per student.

I have so many people to thank for their contributions to this endeavor that I hardly know where to begin.  First, I’d like to thank all the fans of the first book, Regents Physics Essentials (RPE), and fans of the APlusPhysics website.  It was your requests, feedback, and encouragement that prompted the writing of this book.  Following the release of RPE, reader response was tremendous, and your requests for a similar book extending beyond the scope of the NY Regents Curriculum that could be used in physics classrooms across the country as well as for standardized test preparation made the development of this book a personal necessity.

Second, I must thank my two outstanding editors, Jeff Guercio and Joe Kunz, who graciously took many hours out of their busy lives to help make this book (and Regents Physics Essentials) clear, concise, and readable.  I’d also like to thank my student Emily, who first proposed turning our course notes into a review book, and Andrew, who reinforced that you can do anything if you set your mind to it.  I’d also like to thank Muse, whose enthusiasm for this book has been contagious.

Last, but certainly not least, I’d like to thank all the teachers and professors who contributed to this endeavor.  In attempting to write a physics book that would serve the needs of Honors Physics students across the country (and beyond), the input of these teachers and professors has been instrumental in tailoring this book to the needs of a majority of students, while at the same time keeping the length (and cost) low enough to remain attractive to its intended audience.

I’ve enjoyed working on this project throughout the past two years, but as in any extended project, I’m breathing a sigh of relief to have reached the finish line (at least for now).  I hope you find the APlusPhysics website and family of resources a useful tool in your study / instruction of physics, and I look forward to growing our online learning community in the coming years.  Thank you, thank you, thank you, and best wishes on an amazing 2012!

AP-C Review Book Under $10

Posted on by — No Comments ↓

Amazon drops price on AP-C Physics Review Book, now under $10!  A great idea to help prepare for the mid-term and as a chapter-end review…

[amazon_enhanced asin=”0375427325″ container=”” container_class=”” price=”All” background_color=”FFFFFF” link_color=”000000″ text_color=”0000FF” /]

Toilet Paper Rotational Motion Challenge

Posted on by — No Comments ↓

In his Dec. 17 Action-Reaction blog post titled “Falling Rolls,” Frank Noschese details an exercise from Robert Ehrlich’s book Why Toast Lands Jelly-Side Down.

The exercise, a rotational motion problem that challenges students to find the ratio of heights at which you can drop two identical toilet paper rolls, one dropped regularly, the other dropped by holding onto the end of the paper and letting it unroll, such that the two rolls hit the ground at the same time. It’s a terrific, easy-to-replicate and demonstrate problem that pulls together a great number of rotational motion skills –> finding the moment of inertia, applying the parallel-axis theorem, identifying forces and torques from free body diagrams, and converting angular acceleration to linear acceleration. My students dove into the challenge with zest last year, and we decided to repeat the exercise this year, working in groups of two or three to see who could derive the appropriate relationship most accurately.

To begin the exercise, we set our variables (H=height for dropped roll, h=height for unrolled roll, r = inner radius, R = outer radius), then identified the time it takes for the dropped roll to hit the ground using standard kinematics:

{t_{drop}} = \sqrt {{{2H} \over g}}

Next, we did the same thing for the unrolling toilet paper roll:

{t_{unroll}} = \sqrt {{{2h} \over a}}

Of course, if we want them to hit at the same time, the times must be equal, therefore we can show:

{H \over h} = {g \over a}

Obviously, what we really need to focus our efforts on is finding the linear acceleration of the unrolling roll. To save ourselves some time, we started by looking up the moment of inertia for a cylinder:

I = {\textstyle{1 \over 2}}M({r^2} + {R^2})

Using the parallel-axis theorem to account for the unrolled roll rotating about its outer radius we find:

I = {\textstyle{1 \over 2}}M({r^2} + {R^2}) + M{R^2} = {\textstyle{1 \over 2}}M({r^2} + 3{R^2})

Next, we can use a free body diagram to identify the net torque on the roll as MgR, and use Newton’s 2nd Law for Rotational Motion to find the angular acceleration:

{{\tau }_{net}}=I\alpha \Rightarrow \alpha =\frac{{{\tau }_{net}}}{I}=\frac{MgR}{0.5*M({{r}^{2}}+3{{R}^{2}})}=\frac{2gR}{{{r}^{2}}+3{{R}^{2}}}

Since linear acceleration can be found from angular acceleration multiplied by the radius of rotation (R):

a = \alpha R = {{2g{R^2}} \over {{r^2} + 3{R^2}}}

Finally, since we’re looking for the ratio of the dropped height to the unrolled height:

{H \over h} = {g \over a} = {g \over {{{2g{R^2}} \over {{r^2} + 3{R^2}}}}} = {{{r^2} + 3{R^2}} \over {2{R^2}}} = {3 \over 2} + {{{r^2}} \over {2{R^2}}}

For a toilet paper roll of inner radius .009m and outer radius R=.0385m (our school rolls from the janitor supply closet):

\frac{H}{h}=\frac{3}{2}+\frac{{{r}^{2}}}{2{{R}^{2}}}=1.5+\frac{.009{{m}^{2}}}{2*.0385{{m}^{2}}}=1.53

Check out our high-speed video confirmations from 2010 (below)

 

and from 2011 (below)!

 

New Release: Honors Physics Essentials

Posted on by — No Comments ↓

HPE-Cover Honors Physics Essentials is an easy-to-read guide to algebra-based introductory physics, featuring more than 500 worked-out problems with full solutions and covering topics such as: kinematics, dynamics, momentum, impulse, gravity, uniform circular motion, rotational kinematics, work, energy, power, electrostatics, circuits, magnetism, microelectronics, waves, sound, optics, thermal physics, fluids, and modern physics.

This book is designed to assist beginning physics students in their high school and introductory college physics courses as an invaluable supplemental resource in class as well as a review guide for standardized physics assessments such as the SAT Subject Test in Physics, PRAXIS Physics, AP Physics, and CST Physics exams.

Honors Physics Essentials is integrated with the APlusPhysics.com website, which includes online question and answer forums, videos, animations, and supplemental problems to help you master high school physics.