Name__________________________________
Activity
Physics 206
Mr. Dristle
The Mu of the Shoe
(Consumer Product Testing)
Purpose: to scientifically compare the grip of at least three different kinds of shoes possessed by
people in your group
Theory: One measure of the quality of the shoes you wear is their ability to grip slippery surfaces.
The coefficient of friction is a way of showing how much friction is available per unit of
force compressing the surfaces together. In this way the coefficient of friction is a measure
of the gripping quality of the surfaces involved.
Strategy: In this activity you will measure the forces of sliding and static friction for each of the
shoes of the people in the group. You also need to measure the normal force pressing the
shoe to the surface it rests upon. Substitution in this equation yields the coefficient of
friction:
µ=
Procedure:
A.
f
N
Measuring the frictional force (dry conditions)
1.
Using a spring balance, measure the maximum force needed to just start the
shoe moving
€ when pulling horizontally upon it from a resting position.
Record the value in the data table.
2.
Using a spring balance, measure the force needed to pull the shoe
horizontally at constant velocity. Record in the data table.
B.
Finding the coefficient of friction
1.
Find the combined weight of the shoe and any other weights you may have
placed in the shoe. Record in the data table.
2.
Using the equation above, calculate both coefficients of static friction and
sliding friction. Record in the data table.
C.
Repeat parts A and B for the other two shoes
Brand/Type
of shoe
Static
Friction
force
Data For Dry Surfaces
Sliding
Normal
Coefficient
Friction
force
of static
force
friction
Coefficient
of sliding
friction
Name__________________________________
D.
Mu of the shoe
Page 2
Repeat parts A, B, and C for a wet or slippery surface.
Brand/Type
of shoe
Data for Wet Surfaces
Static
Sliding
Normal
Friction
Friction
force
force
force
Coefficient
of static
friction
Coefficient
of sliding
friction
Conclusions:
1.
Which shoe had the strongest grip under dry conditions?
2.
Which shoe had the strongest grip under wet conditions?
3.
Make a bar graph that compares the coefficients of static and sliding friction for
the 3 brands of shoes that you tested. You may either graph by hand on your own
graph paper or use Excel to create a graph on a computer. Be sure to include the
graph when you hand this report in.
4.
Explain whether the coefficient of static friction or the coefficient of sliding friction
best applies to the situation of walking across the floor.
5.
What other qualities besides the grip would a consumer want to have in the shoe they
want to buy?
6.
Pick out one other quality (from question 5) and describe how you could
scientifically test for it in a side by side comparison of different brands.
7.
How would you modify this activity for use with elementary age children?