Friction Blocks

This is a fairly simple device for hands on learning.

To investigate what factors effect the force of friction you can make a block with four different types of materials on a block of wood with a hook at attach a spring score or force probe.

For this project you will need:

wooden fence post
hooks
square of carpet
square of flannel
square of faux alligator
dish of water
old paintbrush
gorilla glue

Step 1: Cutting the Blocks

I started with a wooden fence post because that was the only square length of wood I could locate and then cut it into cubes with a chop saw so the edges were very straight.

Step 2: Adding the Materials

What materials you add to the block depend on what you have on hand that has different coefficients of frictions when dragged onto the surface on which you plan to have the students work in the classroom.

I choose to use gorilla glue so that the materials would be firmly adhered. I tried using wood glue about three years ago and the materials slowly peeled off the blocks, I'm hoping that this glue choice will last longer.

Gorilla glue requires that you dampen the surfaces, spread a thin layer of the glue, and weight down or clamp the bond line while its setting. This step is not required with other glues. Make sure you read the specific directions on whatever you choose for your project.

Step 3: Add a Hook

Once you have attached the different materials, add a hook to the block so you can easily pull it with a force probe.

When you drag the block along a surface with a force probe you can pick the static friction force and kinetic friction force off of a graph of force vs. time. Then by weighing the block you can also look at the coefficient of friction for starting motion and continuing motion.

It helps to have at least one per lab group for their investigations.

Step 4: Uses in the Classroom

Once you have a set of these constructed, they make a great tool for inquiry based lesson such as:

- How does the combination of different surfaces effect the magnitude of the force of friction?
- How does adding weight to a block impact the force of friction? (The students can add weights onto the top of the block.)
- How does adding weight to a block impact the coefficient of friction?

and many other investigations as well!