Day 175: Interesting Momentum Problem

Thursday, 18 May 2017

I found this great question in an old textbook and loved it because of how it pulls together multiple topics we’ve learned:

A 300 g ball is dropped from a height of 90 cm and bounces back up to 66 cm. The change in momentum of the ball is

a. 0.18 kg m/s

b. 1.26 kg m/s

c. 2.34 kg m/s

d. 2.52 kg m/s

e. none of the above

In the lead-up to the exam next week, I gave the kids two exam review quizzes this week. Students took the quizzes in class and checked against an answer key. They then took the quizzes home and worked out the correct solutions and turned in a hopefully-perfect quiz. I graded the final result as a quiz grade.

This worked out to be a wonderful exam study tool and the above question was probably the most challenging thing on it.

Day 174: ExamGram

Wednesday, 17 May 2017

So this was interesting — I posted a series of photos on Instagram with exam review questions and egged my kids on to participate by solving the problems. Here is a sampling:

Screen Shot 2017-05-31 at 9.20.58 PM

Day 170: Conservation of Momentum

Thursday, 11 May 2017


Broke out the photo gates for the first time this year.

I’m not a fan of photo gates in my labs because I think the setup time is too expensive for the results. Instead, I have students use video analysis whenever possible. Conservation of Momentum is one of the rare times the photo gates are a good choice. Video analysis would be time-consuming for the number of collisions we need to run.

Day 167: More Rocket Launches

Monday, 8 May 2017


This kid wanted to launch a rocket with multiple engines. I said ok. It wasn’t until he went to hook up the launchers that he realized this wasn’t going to work.

Day 161: Six Flags

Friday, 28 April 2017

We took the entire 9th grade class to Six Flags. There was a new ride in the kids area that went in circles but you have control over this rudder/sail thing. My friend and colleague Henrik brought along a Bluetooth force probe and physics-ed the heck out of it.


This is the Wonder Woman ride at Six Flags.


Yes, my colleague brought his computer to the park.