Some physics problems

Hey all,
I know you wait all week with baited breath for my weekly posts for a relaxing mini-vacation. So, I thought, what better way to facilitate that than to share some physics problems?
As many of you know, I teach physics and astronomy at a few community colleges around San Diego County. Last week I gave the students in one of a physics classes (calculus-based mechanics) a multiple choice activity worth some extra credit. It was 10 fairly involved (though, far from impossible) questions spread over most of what we had done so far. They could use the text, their notes, work in groups, and had an hour and a half. They did fairly well. I was pleased.
Anyway, I thought a few of you might get a kick at trying your hands at some of the problems… and I spent too much time on it to finish the story I wanted to share today. So, enjoy!

The blank test: phys151_reviewsession_va

The solutions: phys151_reviewsession_va_key

If you’re disappointed that it wasn’t a silly test, try this one that I wrote back in 2014 instead:

If you are curious about the python code I wrote to compile different versions of my tests for me, it is available on GitHub:




This week I decided to mashup Grumpy and Thumbelina to bring you Grumbelina!

Available on RedBubble:

The Greathelm Dragon Riders

greathelmlogo1distWhen word came to our village
That in Greathelm had been started
A guild of dragon riders

In the depth of my heart
I knew that I must join them
And become a dragon rider

My walk was hard and the days were long
But I knew it would be worth it
If I could join the dragon riders

I made it to the Greathelm gates
Just three days after I left home
And asked a guard about the dragon riders

I expected he might send me home
Being cruel and laughing at me
Saying “there’s no such thing as a dragon rider”

But he just smiled, wished me luck
And relayed some short directions
To the hall of the Greathelm Dragon Riders

As I approached the guild hall
My stomach began to churn
What if I wasn’t accepted by the guild of dragon riders?

My worry, though
It was for not, for I was accepted right away
To join the dragon riders

They said that I’d be perfect
But I guess that I misunderstood
what it meant to be a dragon rider

Now, after many years of training
I sit here with a dragon on my back
I the mount, he the dragon rider


You can listen to me read it here:


Join the Greathelm Dragon Riders yourself and get a t-shirt, mug, or some other gear!

A comic about Sonya

I have a lot of amazing friends that I have never met, never stood in a room with, and never looked in the eye, though I see them as closer friends than many people that don’t effectively live in my computer.

We all have our internet friends. For me, because I don’t see them in real life, most of their life is a mystery while aspects of their personality bleed through during our interactions. This creates a sort of personality skeleton, while most of their life and actions, facial expressions and tone of voice are left open to creative interpolation and wild extrapolation.

Sometimes this leads to an image of a person that is completely off base, and other times, as I learn more about the person, I realize that I had certain parts right from the very beginning.

One such friend, Sonya Craig, goes above and beyond in an attempt to spread happy. Her character that lives in my head demanded that I draw a comic of the image I have of her day-to-day activities. I think I got this one pretty close to reality.

You can either click here for a PDF of the comic, or you can enjoy the images below… or… both, I guess… but they’re the same thing.


pg 1


pg 2


pg 3


pg 4


pg 5


In reality, she is a fantastic writer (, a talented artist (, and great person to follow on Twitter ( and facebook ( I suggest you read her words, enjoy her art, and engage with her on Twitter.

And, to Sonya, thanks for being so frigg’n rad.