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.
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.
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 resuls.
6. Tape sandpaper to the table top. Repeat steps 2 to 4 and record your resuls.
7. Place pencils horizontally under the book. Repeat steps 2 to 4 and record your results.
: Students will compose a conclusion based on the data from the experiment. This conclusion should relate to the hypothesis which wa written in the beginning of the lab.