Friction Lab:
Name: _________________________________________
The force of friction is a contact force that opposes the motion of an object. You are familiar with
friction as an idea because…well you’ve never experienced anything without friction. What we
are hoping to accomplish in this lab is to scientifically examine friction to come up with a
mathematical model.
Materials:
• 1 piece of 2x4 with a hook on one end.
• A piece of Grip Shelf Liner (placed on one side of the 2 x 4)
• 1 force sensor and Labquest
• Various masses
• String
Part 1: Types of Friction?
1. Flip the 2x4 so that the wood side is in contact with the table and place the 1 kg mass on top
of it.
2. Hook the Force Sensor to hook on the 2x4 using the string. Gradually increase the force with
which you are pulling until the 2x4 begins to move, keeping the force sensor parallel to the
table. Pay attention to the graph as you pull, what do you notice about the force once the
block begins to move?
3. You hopefully noticed the friction changed depending on whether block was moving,
a. Record the initial force:
b. This force is called Static Friction. Write a definition for Static Friction based on
your observations in the lab.
c. Record the force once the block started to move:
d. This force is called Kinetic Friction. Write a definition for Kinetic Friction based on
your observations in the lab.
Part 2: Mass Dependence?
4. In this section you need to determine if the force of friction if effected by the mass of the
object. Use the space below to write a procedure. Include what variables you will change and
which ones you won’t.
5. Use the space below to record your data for kinetic friction. Please organize it in some way
such as in a data table.
6. Does friction depend on the mass?
If so what is the relationship:
.
Part 3: Looking at the Forces
7. Attach the piece of string to the hook along with the force
sensor. Have one of your lab partners pull straight up on
string, not enough to lift the block off the table, as the
block is pulled along. Repeat at least two of the masses
you did in #5.
8. Draw a force diagram in the margin of the paper for the
forces on the block in #7.
9. How did the force of friction change when someone was lifting up on the block?
10. Considering your findings above, does the force of friction still depend on the mass? If yes
explain the supporting evidence, if not explain the refuting evidence and suggest a correction.
Part 4: Coefficient of Friction
11. Flip the block over so the white material is down. Repeat your experiment from #4 and #5.
Record your data below Try this again with the felt (fuzzy fabric) placed underneath).
12. What is the other factor friction depends on?
13. It is possible to assign a value to this. We call it the
Coefficient of Friction, designated by the Greek letter µ.
The system is set up so that µ between rubber and concrete
equals one. As µ increases friction increases, and vice versa.
14. Use your findings from the entire lab to complete the
following sentence:
a. Friction is proportional to