Summarize your findings in a short report of 150 words. Include your hypothesis, observations, data, and conclusions. Be sure to answer the questions below as well as including your findings and thoughts in your summary.

How many coins did it take to pull the bag off the table without the rollers (pencils)? With the rollers?

Why didn't the box slide off the table before you put enough coins in the bag?

What happened differently when you put the rollers underneath the matchbox? Why?

What factors caused a margin for human error in this investigation? What was your margin of error when you repeated this experiment?

What was the coefficient of friction for the matchbox? Would the coefficient vary if you tied the string to a similar object of different mass? What about a different object with the same mass? Explain.

What did you learn from this investigation? Be thoughtful in your answer.

Follow these steps.

1. Fill the matchbox with pebbles. Weigh the matchbox with the pebbles inside. Record that weight.

2. Tie the string to the box. Allow the string to hang over the edge of the table.

3. Tie the other end of the string to a corner of the plastic bag, leaving an opening to put in coins.

4. Add coins one by one until the box is pulled off the table.

5. Count and record the number of coins and the weight of the bag with the coins in it.

6. Lay the round sticks on the table about 1 inch apart and about 2 inches from the edge of the table.

7. Put the matchbox on the rollers farthest from the edge of the table.

8. Now add coins one by one to the bag until the box is pulled off the table.

9. Count and record the number of coins and the weight of the bag with the coins in it.

10. Repeat the experiment. Determine your margin of error if your results vary. For accuracy, repeat the experiment if desired.

11. Using the equation for the coefficient of friction in the text above, determine the coefficient of friction for the matchbox in each experiment. Include this data in your summary.