University of Virginia
Physics Department

## Styrofoam Helicopters

A Physical Science Activity

2003 Virginia SOLs

• PS.1
• PS.10

Objectives

Students will

• investigate the affects of changing the number of blades and changing the material from which the blades are made affects the speed of a Styrofoam helicopter.

Motivation for Learning

Demonstration-Discrepant Event

Flat Paper vs. Paper Ball

Materials

• 2 sheets of plain white paper

Procedure

1. Make a paper ball out of one of the sheets of paper.
2. Hold both pieces of paper the same distance from the floor and drop both at the same time. Observe. The paper ball should strike the floor first.
3. Ask the students why the paper ball fell faster.

Background Information

The acceleration of a given object is constant over time regardless of the mass of the object. This concept was demonstrated through the comparison of the paper ball and the flat paper. Without wind resistance, both pieces of paper would hit the floor at the same time. The paper ball had less surface area than the flat paper, which reduced air resistance and caused it to fall to the floor first.

This experiment demonstrates the affect of air resistance on styrofoam helicopters. As the number of blades increases, more surface area is added to the helicopter and therefore air resistance is increased. The helicopters with five blades will have a lower velocity than those helicopters with four or even five blades.

The formula for average velocity is displacement/time. The formula for acceleration is (final velocity - original velocity)/time. As a result of completing this experiment, students will understand the concept of air resistance, and be able to calculate velocity and acceleration.

This experiment will take two class periods of 45 minutes. Students should be in groups of no more than four and no less than three. They should complete the data sheet before beginning the analysis questions. After all groups have completed the experiment, have them share their findings with the class and discuss the results.

For the more advanced students, group them together and assign a material that requires the most measuring and cutting, such as note cards. Also, let them try making helicopters with less than three blades and more than five blades if they are ahead of the class. Have them extend their table to include their extra helicopters. For the regular groups, assign the styrofoam plates since this requires the least measuring and cutting. Special needs students should be using feathers since there is no cutting or measuring involved. Choose feathers that are of uniform shape and size.

### Student Activity

Materials

• 2" Styrofoam balls
• Styrofoam plates
• Note cards
• Feathers
• Knife
• Scissors
• Metric Ruler
• 2 meter sticks
• Stopwatch

Procedure

1. Groups will be assigned to a specific material from which to make the blades. If your group is assigned feathers, obtain 12 feathers. If your group is assigned styrofoam, obtain 3 styrofoam plates. If your group is assigned note cards, obtain three note cards.
2. Obtain styrofoam balls and other necessary materials.
4. If your group is using note cards or styrofoam to make the blades, cut 12 blades into rectangular shapes with dimensions 2 cm x 7.5 cm each.
5. Using the knife, cut slits in the styrofoam balls wide enough to slide the blades into tightly. Cut into the helicopter at approximately a 45-degree angle with the plastic knife. Make the cuts at even intervals in an end-to-end style near the top of the helicopter. Cut three slits in the first helicopter, four in the second and five in the third.
6. Insert the note card blades and styrofoam blades into the slits.
7. If your group is using feathers, insert three feathers in the first helicopter at approximately a 45-degrees angle. Insert four feathers into the second and five into the third in the same way.
8. Tape two meter sticks together so that they measure two meters together. This is the height from which you will drop your helicopters.
9. While one person holds the meter sticks, a second person drops the helicopter. Once the helicopter is dropped, another person measures the time it takes for the helicopter to reach the floor with a stopwatch. Time should be measured to the nearest tenth of a second.
10. Repeat step nine three times for each helicopter and record results in the table provided.
11. When all trials are completed and data is recorded, calculate the speed of each drop.

Data Sheet

 # of blades 3 4 5 Trial 1 time(s) Trial 2 time(s) Trial 3 time(s) Total time Avg. time Distance (cm) Speed (cm/s) Acceleration

Height of drop (cm)_____________________

Hints:

Average time = total time/ 3

Speed = distance/time

Acceleration = (final velocity - original velocity)/time

Speed is how fast something is going.

Velocity is how fast something is moving in a given direction.

Students with Special Needs

This activity is accessible to most students; though if a student is unable to manipulate small objects comfortably, the students within the groups may not be able to rotate through all jobs assigned.

Click here for further information on laboratories with students with special needs.

Assessment

1. Did all of your helicopters reach the floor at the same time?

2. Which helicopter reached the ground first? Why?

3. Which helicopters had the lowest velocity? Why?

4. Did the number of blades affect the velocity/speed and acceleration of your helicopters? If so, how?