Monsanto Fund Grant Project Follow-up Activities and Demonstrations

Activity Name / Sneaker Friction 2 day lab & write-up
Participant Name / Bonnie Ekle
Date / 4/2/09
Materials / CBL w/force probe, 3 or more different types of sneakers, 6 or more large paper clips, masking tape, builders sand, plastic drinking cup, balance, spoon, water, pencils
Description / Students are to firmly tape paperclips (in hooked formation) to the front, back and side of a sneaker, being sure to keep paper clips as close to the sneaker base as possible.
Place the cup into the sneaker, and fill the cup with sand until the sneaker and sand masses to 610g. Attach the force probe to the back of the sneaker and test starting/static friction by pulling the sneaker back.
Test sideways stopping friction by pulling from the side clip with a constant pull.
Test forward stopping friction by pulling on the front paperclip with a constant pull.
Finally test fluid friction by placing a small puddle of water on the table under the sneaker and retesting the above frictions and observe the differences.
Rolling friction can also be tested at each pull by placing pencils under the sneaker and again pulling with the force probe.
With each pull, run 2-3 trials, as time allows, and calculate average frictions.
Results / Students should observe that different types of sneakers are better at different types of friction. (running/starting friction, basketball/stopping, tennis/sideways) Students will also observe that the force of friction acts in the direction opposite of motion.
Problems / Tape must be secure or clip may release, and if clips are not low on shoe, the shoe will not pull evenly. Sand becomes messy, but it works better than pennies, wood blocks or weights (all of which we have tried). Some students also try to leave the classroom with paper clipped sneakers. We had used spring scales in the past, but the CBL’s are able to more accurately catch static friction.
Pre/post test results / Students identify independent, dependent variables, identify starting, stopping, rolling and fluid frictions through the variety of paperclip placement. It is also important that they are able to identify all the forces acting on the sneaker, in addition to the force of friction. They will also be able to identify at what time forces are balanced or unbalanced, throughout the lab.
Student Comments / Students completely enjoy this lab, as they get to work with each other’s shoes. It is one of our most memorable labs in 7th grade science.