Activities · In My Class Today · New Teacher

3 Ideas for a Strong Start

It is the end of July, the back to school sales have been running for a month, the #clearthelist movement is in full force. While I keep telling myself I have ALL of August left (that’s actually a lie, I have institute the 30th/31st) many of us are starting in just a few weeks. Here are three ideas to start physics strong. These ideas are grounded in my values and beliefs around teaching physics. You can read about those here

Physics is about EXPERIMENTS

I want students to know science is investigative and that anyone can do it. Many teachers will do a team-building activity on the first day, but I prefer to let students play. This gives me a chance to observe the dynamics of each class before I begin to influence the room and it also takes any pressure off of students to perform for one another or myself. I try to set up a demonstration or lab from each of the units for the entire year. Directions for observations are left on a notecard in front of the set up. Students are asked to write down detailed observations about each demonstration. Over the weekend I ask students to find the demonstration online and learn about how it works. Students are then asked to write a claim, evidence reasoning statement about a single demonstration. Here is my handout and some of the demos I set up

Getting to Know You

When we begin class I ask students to introduce themselves, rather than butchering their names on the roster. I take notes for myself. I ask students to share their name, and how they are feeling. I will also ask them to create a flipgrid introduction with a little more info. This allows me to have their pronunciation recorded so I can review it repeatedly. Here are the prompts:

1) State your first and last name
2) What is something you’re really into, or “your thing?” This could be an interest, hobby, job, talent, etc… anything!
3) Post a picture in your video of you doing your thing or a product from your thing
4) What is one thing you wonder about one (or more) of the demos from the first day? (I wonder why….)
5) Respond to at least TWO classmates!

Physics is for Everyone!

I am a STEP-UP advocate and one of the lesson plans in the program is the Careers in Physics. In the lesson students learn about the vast scope of employment opportunities with a physics degree and then are asked to create a career profile. Students do this by taking a super short survey where they check off their interests and values and then they are matched with a professional who shares their interests. You can access the lesson plan and resources here.

I hope you find these ideas useful! What else have you done to set the tone for the year? Drop it in the comments!


Souped Up Soup Can Demo

At an AP Institute I was introduced to the demonstration where you roll different cans down a ramp and a can of broth is ridiculously fast compared to others. The reason, of course, is that the low viscosity of the broth means the liquid does not spin. In turn the fast majority of the can + contents has translational energy only.

I wanted to do something more with this excersice than “guess which is which”. After some poking around I settled in on this lab that I now run each year. Be forewarned: the results aren’t spectacular, but the lab comes back with great data and a great experience. Students regularly report this is their favorite activity of the year.

We start by laying the foundation of the race. I have 5 cans: An empty can with the lids off, an empty can with lids, refried beans, condensed cream of mushroom soup and chicken broth. I provide students with the following information and ask students to rank by which gets down the fastest.

We share results and comment on similarities. Groups generally predict the empty can without lids will be last, but the rest gets messy. Did students put the refried beans because it was a cylinder or because it has the greatest mass? Where do you put the broth (many throw it in the middle). The cream of mushroom soup has a smaller diameter.. how does that matter? We’ve talked about all of this already, this is a great application.

After our discussion (mass is irrelevant, radius is irrelevant) we talk about modeling each can. The empty cans and the refried beans are obvious: hoops and cylinders. But what about the mushroom soup? When you dump it out you get a cylinder of soup in the pot, so it’s like a hoop + 2 disks + a cylinder of soup. We race the “obvious” ones…empty vs beans, empty + lids vs mushroom soup. Then we race the winners and losers… empty first. I poll the class about the beans and soup. It’s a 50-50 split. I tell them this is a good guess. We have tot race best 2 out of 3. Beans wins by a hair.

Then enter the broth.

After broth is the hands down winner, we talk about what’s happening. What is the liquid DOING? (Many studnets think itt’s spinning like a hoop). I demonstrate with a VOSS bottle and dyed water (VOSS is nice and smooth).

For homework I ask students to develop an expression for ANY object down the ramp. How can we do this? Well one thing worth noting is that every moment of inertia is some object MR². So let’s replace “some number” with k. I tell students they need to figure out the expression and what they will plot to yield a straight line and what the slope will represent.

The next day we review student work. It’s a cool derivation.

We get down to the fact that students need a graph of v² and height. Ok cool. But how will we compare our results? We go back to the models. Students are responsible for coming up with the velocity at the bottom of the ramp for their assigned can. For this activity I put students in ability-level groups, assigning the empty cans and the beans to the students who are usually C and lower, the broth to my B students and the mushroom soup to my A students. (more on that choice another day). After students have a chance to work through their derivation we review all of them. One of the things we discuss previously is that when determining velocity at the bottom it’s always the √number*g*h and that number is between 1 (hoop) and 2 (sliding only). The numbers we get all fall in line with our expectations and observations…including why mushroom soup and refried beans are such a close call!

Student work for can of chicken broth.

Before we begin the lab we need to have a discussion about reducing error. We have a major problem. Height is easy enough to measure with little uncertainty, but we are looking at an expression with final velocity SQUARED. This is problematic for several reasons. First, the square means that uncertainty is going to propagate and blow up. Second, we’re looking for FINAL velocity. Cherry-picking that data point is sure to be messy with tons of uncertainty and, frankly, a waste of our tools. So what IS consistent and reliable no matter what we do? Students quickly realize it’s acceleration! We know how to best collect that data from other labs: run a regression through the position or velocity graph. We can then use a spreadsheet to manually calculate the expected final velocity for a specified distance.

Students are able to get data that generates amazing straight lines and then they use that data to determine the moment of inertial of their cans.

Student data for chicken broth

Some of the cans will be pretty far off from the theoretical models, but that’s ok! We tried to really simplify something real and complex! (The original idea from which I got this the activity used cans filled with concrete and other materials that are much closer to the models.)

For the full activity and handouts, I’m sharing here!

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