## Sunday, April 18, 2010

### Friction Test

Our final study of Energy (Motion) came with an experiment to help students practice using a spring scale. This experiment, called Motion 7, was a total bust. I don't recommend it at all. Which doesn't mean that the nice people at NEED don't know what they're doing -- simply that it didn't work for my group. So tomorrow we are doing a variation. Here's my plan:

First, the students are to get in groups of two. This is because one person needs to be pulling on the spring scale and the other person reads the force. With their partner, the children are to list all the surfaces they can think of in or around the school that we could drag our block of wood across. (I simply went to the hardware store and asked for some scraps, then screwed a screweye into one end of each piece of scrap wood so that the spring scale can be hooked onto it.) Some example might be: tabletop, carpeted floor, tile floor, mulch, grass, blacktop

Next, they are to list the surfaces in order of how much friction they predict each surface will exert on the block, in order from most friction to least friction. This is the Hypothesis step.

Third, they are to work with their partner to test each surface TWICE and measure the amount of force needed to overcome friction and get the block to move. Obviously, they can't switch wooden blocks with another team halfway through, so they need to continue to use their same piece of wood.

Fourth, they are to analyze their data by creating a bar graph on graph paper. Each surface will have two side-by-side bars, one bar for each test on that surface. This will allow the students to compare the surfaces more easily.

Finally, they are to present the results of their data by rewriting their list of surfaces in the correct order of Friction, from most to least. And share it with the class.

Friction goes along with our discussion of Newton's First Law and Inertia.