# Day 112: Video Analysis on Repeat

Wednesday, 8 February 2017

“Hey kids, I’m going to teach you to predict the future! You can use video analysis to learn about an object’s motion, and assuming it keeps going like that, you can predict details of its motion beyond the short length of track pictured here.”

“So, go get a cart, a track, and your phone. Tell me the acceleration of your cart.”

Where in the past, I relied on more printed labs with detailed procedures, this year, I’m taking a page from the physics teachers of the internet and focusing on representing motion multiple ways. We’ve done three video analysis labs, and every time I ask the kids to divide their papers into four quadrants: describing the motion in words, on a data table, in a graph, and with an equation.

It’s paying off. Pretty much everyone could set up the video analysis in their videos. I even showed them intermediate tricks like setting the coordinate system in a convenient way (like, having the x-axis run along the length of the track).

Then I gave them a quiz on inferring motion from reading graphs. We had near-perfect results with these questions:

1. Describe the motion on each graph as “object moving forward/backward” AND as “object maintaining/increasing/decreasing speed”.
2. Then, I asked them to match up these velocity vs. time graphs with the position vs. time graphs above.

You gotta do stuff a bunch of times for it to be a skill everyone in the room has. That’s why we video analyze all the things this month.

# Day 108: What is Free Fall?

Tuesday, 31 January 2017

I wanted to teach them video analysis so they dropped golf balls and learned a little about freefall as well. Later, we went outside and I chucked a bocce ball as high in the air as I could. They filmed it:

I try to get the students to understand plotting position and scaling on the first go around. These days, I try to do most kinematics labs using video analysis only (as opposed to breaking out the motion detectors or photogates). I do that because the kids get pretty darned good at video analysis after we’ve done it a bunch.

Pro tip: though your computer has a built in camera, resist using it for video analysis. The frame rate and resolution aren’t that great.

By the way, my video analysis software of choice is Logger Pro because it comes preloaded on the student computers. A good free alternative is Tracker.