Physical Science: Final Day of Testing

Students wrapped up testing their designs and started to work on a sales pitch to convince the project’s (imaginary) customer that their design should be scaled up into the real thing. One group’s duct tape came loose, which meant the cup holding their egg fell off in most of the collisions. I was very pleased when they suggested that might reduce the force the egg experienced and managed to use Newton’s 2nd Law to explain why that would be.

Testing a t-bone collision

Physics: Spring Force Lab

Students collected data to find a relationship between the force a spring exerts and how much it is stretched. I had the spring scales still out from another lab, and many students used them as a handy hook to hang their springs from. Several students commented that the reading on the spring scale consistently matched the force exerted on the bottom of the spring. I’m looking forward to revisiting that when we get to Newton’s 3rd Law later this week.

Physical Science: Testing Again

Students tested the second iteration of their designs. This time around, groups had to plan three of their own tests, rather than doing the ramp test I’d devised for the first round. During the testing, each group also had to serve as an evaluator for another group’s tests. They were tasked with providing feedback on the validity of the tests and making their own assessment of whether the design passed each test.

Using dry ice to simulate skidding on a slippery road

Straw bumpers that went all the way around the car to protect against a range of collisions

Physics: Friciton

This week is about looking at some specific forces, and we started with friction. Students brainstormed what variables might affect how large the force of friction is, then came up with simple experiments to test a few of those variables. Groups measured the force of friction by pulling blocks along with spring scales, which opened the door for some good discussion on uncertainty. Every group did several trials for a given condition, then took an average. Several groups initially said that certain variables, such as surface area, had an impact because their average force was different for each condition. I got one of these groups to share their surface area data with the rest of the class for a closer look. While we haven’t covered uncertainty in this course, students were able to see that the range of forces measured for a given surface area was greater than the difference between the two averages. This lead students to conclude that the difference was probably not meaningful. Its a shift for students to think about the physical meaning of the numbers they are working with, whether in the lab or in a problem set, and I was pleased to see some evidence of that shift in the discussion of this data.

Physical Science: Redesign

Now that groups have a plan for how they will test the second iteration of their design, they worked on actually planning that design. Compared the first time around, there was a lot more conversation about the different ways designs could fail. There was also a lot of talk about what had and hadn’t worked in the first iteration. At the end of the hour, each group paired up with another to share their testing plan, their design, and a justification for their design.

Physics: Free-Body Diagrams

After a quiz, students took their first shot at drawing free body diagrams. A lot of conversations went back to yesterday’s bowling ball lab to try and decide what kinds motion did or did not require a force.