At the beginning of the class, students talk about whether a person or a toy car would go down a slide faster. A student says that the toy car would win because the person's shoes would slow the person down. The class decides to do the experiment outside in the playground.

Some things to notice: (click to hide)

Brittany reasons that because people wear shoes, they would be less slippery (going down the slide) than toy cars. To determine if shoes do make a difference for people going down a sliding board, Kyleigh suggests doing the experiments twice, once with shoes and once without shoes.
The students decide that they want to conduct an experiment to see (1) if shoes will cause a student to go slower down a slide and (2) if a heavier thing (student) will fall faster down a slide than a lighter thing (car). They deal with issues of experiment design including choosing variables to test (boy with shoes vs. boy without shoes, and boy vs. car), how to measure their observations (counting vs. sand timer), and how to get accurate and precise results (Jose brings up issues of human error in flipping the sand timer, Alexis asks to run multiple trials).

The students decide that they would have one trial with the person wearing shoes and one with the person not wearing shoes. They go outside to do the experiment.

After the class returns to the classroom, Sharon has a discussion with several students about what impacts the speed of a car going down a ramp. Jamir claims that a car will go faster down a steeper ramp and Sharon challenges him to prove his claim. After a few failed attempts, he finally gives her a satisfactory justification when he appeals to a limiting case argument—when you put the ramp flat on the floor, the car won't move at all. Jennifer and Jose argue that Gustavo went slower than the car because his clothes are rough and the wheels of the car are smooth.

Sharon also has a discussion with several students about whether heavy or light objects would fall faster. Pricila talks about how heavier objects fall faster than lighter objects. As an example of a light object, she talks about a feather and describes how gravity makes it go back and forth as it falls. She says gravity is like a machine that pushes down, similar to what a student had said the previous day. However, in the case of the feather, gravity decides to leave the feather alone as it falls, which is why it falls slowly. A little later, Pricila returns holding a wet towel and a dry towel. She drops them at the same time, showing that the wet towel falls faster, trying to support her claim that heavier objects fall faster. Then, to further support her claim, she gets two plastic containers, fills one with a little water and the other with much more water, and shows Sharon that the latter is much heavier.

Some things to notice: (click to hide)

Priscila devises a beautiful experiment to support her claim that "weight matters" for how fast something falls. She drops a wet paper towel and a dry paper towel, and observes that the wet towel falls faster than a dry towel. She even goes a step further to show that wetting a towel is a legitimate method of adding weight by comparing the weight of an empty cup to a cup full of water.

Day 13