University of Virginia
Physics Department

## Experimental Design

A Physical Science Activity

### Student Activity

Materials (for each lab group)

• Ruler
• Eight textbooks
• Paper cup with handle (handle can be made out of string)
• Approximately 75 pennies
• 9 strands of spaghetti

Procedure

1. Use the ruler to place the two stacks of books 10 cm apart.
2. Gently hang the cup from one strand of spaghetti.
3. Place the spaghetti on top of the books to form a bridge.  The cup should be hanging down between the stacks of books like a bucket.
4. One at a time, add pennies to the cup until the spaghetti breaks.
5. Record the number of pennies needed to break the spaghetti in Data Table 1.
6. Repeat this procedure 2 times and record the number of  pennies in the data table.
7. Now use the ruler to place the stacks of books 15 cm apart.
8. Repeat the above procedure three times and record the number of pennies in the data table.
9. Finally, use the ruler to place the stacks of books 20 cm apart.
10. Repeat the above procedure three times and record the number of pennies in the data table.
11. Cleanup - be sure that all pieces of spaghetti are placed in the trash can - not in the sinks or on the floor! ! !

Data Sheet

 Distance Between Books Number of Pennies Required to Break Spaghetti Trial #1 Trial #2 Trial #3 Average 10 cm 15 cm 20 cm

Experimental Design

Fill in the following:

• Independent Variable

• Levels of the Independent Variable

• Dependent Variable

• Control

• Constants

• Repeated Trials

Assessment

1. Make a statement about how the distance between the stacks of books affects the number of pennies needed to break the spaghetti.

2. Why did you do three trials and find the average?

3. Why is it important to use the same type of spaghetti for each trial?

4. Why are constants important in an experiment?