# Monkey and the Hunter Conceptual Explanation

Back in mid-November, I posted to my 180 blog about the classic monkey and hunter demonstration. In that post I referenced a conceptual explanation as to why the hunter should aim directly at the monkey. Andy asked me to share the conceptual explanation and I’m finally taking time to do so.

For many years the best conceptual explanation I could offer was based on that of a student who came up with the following after seeing the demonstration. Imagine there is no gravity. The angle is such that in the time it takes the projectile to move horizontally, it will move the necessary vertical distance to hit the monkey. The effect of adding back gravity just adds the $\frac{1}{2} a t^{2}$ part of the equation which is the same for the monkey and the projectile.

This year, I developed an alternative conceptual explanation. Put yourself in the frame of reference of the monkey. The difference in the vertical component of the velocity between the monkey and the projectile is the same and will remain the same due to the acceleration of gravity. Therefore, the projectile has a constant velocity and, if aimed directly at the monkey, will move in a straight line toward the monkey.

I received a GoPro for Christmas and plan to use it to film this demonstration from the perspective of the monkey.

# CSEd Week

Due to space availability, we held our Computer Science Education Week activities a week early. My colleague and I and our students shared student work over three days in the cafeteria. We highlighted robotics, art, and games over the three days. We also provided the opportunity for students to participate in the Hour of Code. My colleague, @Mr_Alesch, created the following poster to promote our activities:

I created the following video to promote computer science:

A handful of students completed the Hour of Code and many more students saw what students in the various computer science classes created. It was a good outreach activity and we learned how to make it even better next year. Students enrolling in computer science classes appear to be increasing; hopefully, this helped.

# Physics Capstones

This year’s AP Physics B capstones were as great as last year’s. Click there to read more about how I structure capstones.

• Joe’s GravitON â€“ A Python based N-Body Gravity Simulator. Cleanly implemented and well documented VPython implementation of the n-body problem. Can’t wait until Joe offloads process to the GPU!
• Danny’s Resistance Bands vs Free Weights. A well-designed experiment to model resistance bands.
• Andrew’s Amateur Kitchen Rocketry. Very creative. Have you ever considered building an olive-oil-powered rocket?
• Helen’s [Springboard Diving](Amateur Kitchen Rocketry). Great video analysis and fantastic video interviews of coaches and divers.
• Matt’s Pony Physics: Very creative and thorough exploration of the physics of My Little Pony.
• Andrew’s Rifle Toss: wonderful application of more advanced physics to determine the energy needed for an 8-rotation rifle toss. (Web page struggles to display the equations; refer to PDF at the bottom.)
• Nathan’s Physics of Intonation: answers the question “how important is it to play in tune?” Includes a Python script that calculates superposition and a great Minute Physics-style video.
• Nathan’s Putt Simulator: Models the motion of a golf ball on a generated surface. Incredible application of calculus and computational modeling. (Requires Python, VPython, and Matplotlib.)
• Michael’s Tunnel to the Center of the Earth: Wonderful Minute Physics-style video supported by Excel-based computational models. Cites Rhett Allain’s How Long Would It Take to Fall through the Earth, solves Rhett’s homework, and then assigns his own.

Based on feedback from students, I’m going to make a one change for next year. Several students actively peer reviewed each other’s capstones. This was fantastic and improved the quality. I wanted to make this a required activity next year.

I think this year’s class benefited from seeing examples from last year’s class. Now that I have a diverse collection of excellent capstones to share, students have an easier time understanding what a capstone is and how to present it in an engaging manner.