Activity

# Friction of Different Surfaces – Lab

## Students who are blind or visually impaired measure the force necessary to move a book over various surfaces and determine relative friction.

Friction, simply described for students in elementary school is any force that slows or stops motion.   In this lab, students compare the force necessary to move the same object over various surfaces.  The relative friction produced by these surfaces can be determined and compared.  Surfaces producing greater friction require more force to move the object while surfaces causing less friction require less.

I find this lab to be elegant in its simplicity.  It is appropriate for both elementary and middle school students, as well as high school students on a modified curriculum.   For an engaging friction lab more appropriate for high school students, please see a recently posted activity by Stu Grove: https://www.perkins.org/accessible-science/causes-friction-surface

### Materials

• print or braille table for results (See attached or download here)
• 24″ piece of string
• small paperback book
• large paper clip
• small metal washers
• waxed paper
• sandpaper
• pack of unsharpened pencils

### Preparation

Materials prep for this activity involves only gathering the materials and preparing the simple table on which students will record their results.

Most of the materials will already be in many science labs.  I keep these materials stored in a labeled box for use year after year.

### Procedure

After reading over the lab procedure, have students propose a simple hypothesis as to which surfaces will cause greater friction and which will cause less friction.  Discuss with each student his/her reasoning for the hypothesis.  Students should write down their hypotheses to compare with the lab results.

#### Lab Procedure:

1. Tie the ends of the string to make a loop.  Put the loop over the front cover of the book.
2. Place the book on the table about 4 inches from the edge.  Let the loop of the string hang over the edge of the table. See picture below.

3. Straighten the paper clip to form an S- shape.  Describe the S shape or use a piece of Wikki Stix (http://www.wikkistix.com/) to make an “S”  for students not familiar with print letters.  Tie the paper clip onto the string.  This makes adding washers easier and keeps the paper clip from slipping from the string.  (Assistance may be necessary for this step.)

4. Put a small washer on the paper clip.  Add washers one at a time until the book begins to move.  Record the number of washers needed to move the book in the table.  When necessary, students should place one hand gently on the edge of the book to ascertain when the book begins to move.

5. Tape waxed paper to the table top.  Repeat steps 2 to 4 and record your results.

6. Tape sandpaper to the table top.  Repeat steps 2 to 4 and record your results.

7. Place pencils horizontally under the book.  Repeat steps 2 to 4 and record your results.

#### Closure

Students will compose a conclusion based on the data from the experiment.  This conclusion should relate to the hypothesis which was written in the beginning of the lab.

### NGSS Standards:

Forces and Interactions: PS2A

The motion of an object is determined by the sum of the forces acting on it; if the total force on the object is not zero, its motion will change. The greater the mass of the object, the greater the force needed to achieve the same change in motion. For any given object, a larger force causes a larger change in motion. (MS-PS2-2)

Forces and Motion: PS2A

Newton’s second law accurately predicts changes in the motion of macroscopic objects. (HS-PS2-1)

By Laura Hospitál

This lab was adapted from the Pacemaker General Science Book, 3rd Edition, Pearson Education, Inc., 2001

Pictures by Ditmar Hospitál