With flat-Earthers on the rise, it's a good time to review reality. Paul Hewitt's here to help.
Hewitt-Drew-it! PHYSICS 149. Eratosthenes and the round earth
Hewitt presents an easy explanation on how Eratosthenes measured the diameter and circumference of the earth in about 235 B.C. Only simple geometry is used.
For a complete index of Hewitt Drew-It video lessons, start at
Hewitt Drew-It! PHYSICS Screencast Directory
There are quick lessons on virtually all topics covered in introductory physics, conveniently organized for easy access.
Friday, December 29, 2017
Tuesday, December 26, 2017
Making engagement visual
At semester's end, it's possible to look back and see how student engagement in the course manifested itself into semester grades.
Students who perform well on tests and labs naturally percolate to the top. But those who don't excel in those objective measures have alternate routes to good grades in my courses.
During the semester, "extra credit" (credit toward the final: CTF) is awarded in dribs and drabs for various tasks and in-class competitions. Completing paperwork associated with the beginning of the school year and team performance in our egg-toss competition are typical first-semester sources. The credit is accumulated through the semester, but only becomes active as an addition to the final exam score. Some teachers add in extra credit as it comes in. That leads to disappointment when final exam scores are low. Adding it to final exam scores at the end of the semester leads to delight similar to finding money under the cushions of the sofa/couch/davenport.
More importantly in my Physics (PHY) and Conceptual Physics (CP) courses, students can earn back points lost on unit tests. The process is called Test Correction Journal. Students write "journal entries" for each item they missed on a unit test and reflect on why they were drawn to a wrong answer over the right answer. Later, a quiz is given consisting of questions from the original test. If they get 10 out 10 on the quiz, they earn back half the points they missed on the test. If they 9/10, they get 90% of half the points they missed, etc.. A 60 can turn into an 80 and 40 into a 70. A 90 can turn into a 95. The more help you need, the more help TCJs provide.
Neither CTF nor TCJs depend on rapid assimilation of course content. But they do depend largely on engagement. Sometimes students who miss many items on a unit test cannot finish the journaling process that we begin during class time. They need to come it at lunch or after school during an approximately two-week window to finish the journal. Only students with completed journals are allowed to take the quiz that will earn their missed test points back.
Students who disengage from TCJs create and expand a gap between themselves and those who are engaged. My engaged students earn only As and Bs. But Cs, Ds, and Fs are given every semester, as many students elect to disengage.
The listings below are actual student data. Each is a period, sorted by points earned. I used Excel's conditional formatting to color the cells in a spectrum from top-score green to bottom-score red, with yellow in between. The next column colors CTF points on a same basis (green good; red bad). Then (for PHY classes), it's the TCJ column with the same color scheme. The last column shows the final exam raw score out of 50. The top number in each column show the maximum value possible.
The pattern is fairly consistent, with anomalies here and there. Nothing to shatter the Earth here. I just wanted to see how well the seemingly nebulous "engagement" tracks to overall class performance. Teachers know this pattern is really the only one that's possible. Students don't always have an intuitive understanding of it. Some will see the evidence and reject it nonetheless.
Those students believe it's possible to get a top score with minimal engagement. It's mathematically possible. It just never happens. They may also fear that investing in full engagement will not be rewarded in a top score. Yet we don't find a red Points value followed by green CTF and TCJ columns. That's actually much less mathematically possible, given what TCJs do.
Students who perform well on tests and labs naturally percolate to the top. But those who don't excel in those objective measures have alternate routes to good grades in my courses.
During the semester, "extra credit" (credit toward the final: CTF) is awarded in dribs and drabs for various tasks and in-class competitions. Completing paperwork associated with the beginning of the school year and team performance in our egg-toss competition are typical first-semester sources. The credit is accumulated through the semester, but only becomes active as an addition to the final exam score. Some teachers add in extra credit as it comes in. That leads to disappointment when final exam scores are low. Adding it to final exam scores at the end of the semester leads to delight similar to finding money under the cushions of the sofa/couch/davenport.
More importantly in my Physics (PHY) and Conceptual Physics (CP) courses, students can earn back points lost on unit tests. The process is called Test Correction Journal. Students write "journal entries" for each item they missed on a unit test and reflect on why they were drawn to a wrong answer over the right answer. Later, a quiz is given consisting of questions from the original test. If they get 10 out 10 on the quiz, they earn back half the points they missed on the test. If they 9/10, they get 90% of half the points they missed, etc.. A 60 can turn into an 80 and 40 into a 70. A 90 can turn into a 95. The more help you need, the more help TCJs provide.
Neither CTF nor TCJs depend on rapid assimilation of course content. But they do depend largely on engagement. Sometimes students who miss many items on a unit test cannot finish the journaling process that we begin during class time. They need to come it at lunch or after school during an approximately two-week window to finish the journal. Only students with completed journals are allowed to take the quiz that will earn their missed test points back.
Students who disengage from TCJs create and expand a gap between themselves and those who are engaged. My engaged students earn only As and Bs. But Cs, Ds, and Fs are given every semester, as many students elect to disengage.
The listings below are actual student data. Each is a period, sorted by points earned. I used Excel's conditional formatting to color the cells in a spectrum from top-score green to bottom-score red, with yellow in between. The next column colors CTF points on a same basis (green good; red bad). Then (for PHY classes), it's the TCJ column with the same color scheme. The last column shows the final exam raw score out of 50. The top number in each column show the maximum value possible.
The pattern is fairly consistent, with anomalies here and there. Nothing to shatter the Earth here. I just wanted to see how well the seemingly nebulous "engagement" tracks to overall class performance. Teachers know this pattern is really the only one that's possible. Students don't always have an intuitive understanding of it. Some will see the evidence and reject it nonetheless.
Those students believe it's possible to get a top score with minimal engagement. It's mathematically possible. It just never happens. They may also fear that investing in full engagement will not be rewarded in a top score. Yet we don't find a red Points value followed by green CTF and TCJ columns. That's actually much less mathematically possible, given what TCJs do.
Sunday, December 24, 2017
Fun does not mean unprofessional
I follow some great educators on Twitter, one of the great things about the platform is being able to find people that share interests that I don't know personally. I like to follow inspirational teachers that make me want to do better, that can expand my point of view and remind me that how varied and diverse our national education system is. I get a lot of great ideas from physics teachers and get to chuckle in commiseration with hashtags like #teacherlife and #teacherproblems.
Two days ago a math teacher and author from New York Jose Vilson posted a video of himself dancing in class with a great Christmas sweater. I liked it, not thinking much of it and continued to scroll. Unsurprisingly, Jose's video was retweeted by other people I follow so I got to smile again every time it came up:
- Teach students to do the "Superman" yoga pose and worn two back packs at a time while teaching center of mass and stability.
- Literally kicked off my heels to run across my classroom and try to race the stadium wave my students make across the classroom while teaching, duh, waves.
- Spun around like a ballerina/ figure skater to remind them about conservation of angular momentum.
- Spun and leaped in a circle to reinforce the difference between rotation and revolution.
- Stood on lab benches to drop/ throw/ launch a variety of projectiles.
- Channel my inner drill sergeant and lead the class in force exercises; I say "A Force is a what?" and they respond "A push!" I say "And a what?" and they shout back "A pull!"
There are probably more that I've forgotten. As many other teachers have I also frequently share jokes and puns about my curriculum. Students' suspicions are correct, teachers do actually plan some of those jokes. I have a construction hat I've written the formula for work on and I wear it every year. This year I made a giant piece of buttered toast just to illustrate a tough textbook problem
Teachers often use humor to teach and engage their students. We've been known to use comic strips and Dan Burns even dresses up to look like the physics teacher in FoxTrot on occasion.
All of that is acceptable, but dancing is not? You've undoubtedly heard the phrase "Happy Dance," when someone does a little dance for about 10 seconds when they are unexpectedly happy. You may see your students do a happy dance when they got a grade higher than they expected. I've seen full grown adults do a happy dance in a store when they find their favorite wine on sale. The point of the happy dance is spontaneous joy, despite surroundings, in order to celebrate something unexpected or surprising. How is that accepted across our culture but a teacher in a classroom of happy students can't dance? Being fun does not mean you are unprofessional. I say teachers continue the dancing, winging, joking, etc. This job is hard enough without being a sour puss.
Two days ago a math teacher and author from New York Jose Vilson posted a video of himself dancing in class with a great Christmas sweater. I liked it, not thinking much of it and continued to scroll. Unsurprisingly, Jose's video was retweeted by other people I follow so I got to smile again every time it came up:
I was surprised however, when I started noticing that not only were people retweeting the video but also including remarks of defense and support. I had to follow a few threads to figure out why Jose even needed to be defended. (Hint: he shouldn't have to be) There had been comments about Jose's dance being "unprofessional" but they weren't so nice about it, in fact they were downright racist about it.When you’re a teacher about an hour away from vacay and take off the professionalism for a minute pic.twitter.com/6AYlvfDznP— José Luis Vilson, NBCT (@TheJLV) December 22, 2017
On one hand, 2017 can't shock me much more but on the other, he was just dancing! He is a great teacher and activist, published author, etc. but that doesn't mean he's not human. Teachers are human. We are not robots, we are people. The whole thing got me thinking of all the times I've been "unprofessional" in front of my students. Its quite a list:Keep America Racist Forever. https://t.co/rxs6oz2YU6— José Luis Vilson, NBCT (@TheJLV) December 23, 2017
- Teach students to do the "Superman" yoga pose and worn two back packs at a time while teaching center of mass and stability.
- Literally kicked off my heels to run across my classroom and try to race the stadium wave my students make across the classroom while teaching, duh, waves.
- Spun around like a ballerina/ figure skater to remind them about conservation of angular momentum.
- Spun and leaped in a circle to reinforce the difference between rotation and revolution.
- Stood on lab benches to drop/ throw/ launch a variety of projectiles.
- Channel my inner drill sergeant and lead the class in force exercises; I say "A Force is a what?" and they respond "A push!" I say "And a what?" and they shout back "A pull!"
There are probably more that I've forgotten. As many other teachers have I also frequently share jokes and puns about my curriculum. Students' suspicions are correct, teachers do actually plan some of those jokes. I have a construction hat I've written the formula for work on and I wear it every year. This year I made a giant piece of buttered toast just to illustrate a tough textbook problemTeachers often use humor to teach and engage their students. We've been known to use comic strips and Dan Burns even dresses up to look like the physics teacher in FoxTrot on occasion.
Sunday, December 17, 2017
An inclination for serendipity
When I show the Honda Cog ad (flavors of equilibrium, energy transformations), there is always strong skepticism regarding the wheels that roll uphill. So I am always ready to go with the demonstration illustrated in this previous post.
Sometimes I leave the wheel resting comfortably on the inclined plane. That very same inclined plane is also home to my electronic balance.
So why not another Physics Mashup?
First, students should be able to explain why the wheel holds fast on the incline before I spill the beans. Or in this case, ball bearings.
Next, I tare the scale and rest the "hill-hugger" atop the scale. A reading is observed.
Finally, students should correctly predict what will happen to the scale reading when the incline is re-leveled. Assure them the wheel will remain atop the scale.
It's not so novel it will shatter the Earth. But it's nice to milk some mileage out apparatus just otherwise lying around.
The answer can be seen via the comments. I leave the solution to the reader.
Sometimes I leave the wheel resting comfortably on the inclined plane. That very same inclined plane is also home to my electronic balance.
So why not another Physics Mashup?First, students should be able to explain why the wheel holds fast on the incline before I spill the beans. Or in this case, ball bearings.
Next, I tare the scale and rest the "hill-hugger" atop the scale. A reading is observed.
Finally, students should correctly predict what will happen to the scale reading when the incline is re-leveled. Assure them the wheel will remain atop the scale.
It's not so novel it will shatter the Earth. But it's nice to milk some mileage out apparatus just otherwise lying around.
The answer can be seen via the comments. I leave the solution to the reader.
Monday, December 04, 2017
Advanced Studies in Artistic Lightning
Watch it big; watch it loud. But mostly, watch it.
And remember, deviations from physical realism serve not as disqualifies, but springboards for discussion here.
Transient from Dustin Farrell (www.dfvc.com) on Vimeo.
And remember, deviations from physical realism serve not as disqualifies, but springboards for discussion here.