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TE Activity: Heavy Helicopters

Students learn about weight and drag forces by making paper helicopters and measuring how adding more weight affects the time it takes for the helicopters to fall to the ground.

For safety, speed and fuel efficiency, when designing recreation and transportation vehicles, engineers take into account all forces acting on the object. Engineers consider drag forces when they design land, air and water vehicles. When prototyping objects such as wings, windshields, propellers, helmets, sports equipment, or even an athlete's position, engineers use a wind tunnel to see the drag forces that are created around an object when air moves by, and they adjust their designs to minimize the amount of drag.

Learning Objectives
Materials
Introduction/Motivation
Procedure
Attachments
Safety Issues
Troubleshooting Tips
Assessment
Extensions
References

Grade Level: 6 (5-7)	Group Size: 2
Time Required: 45 minutes	Activity Dependency : None
Expendable Cost Per Group : US$ 1
Keywords: mechanics, acceleration, aerodynamics, aeronautical engineer, drag, force, helicopter, weight

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Colorado Math
- 1. represent, describe, and analyze patterns and relationships using tables, graphs, verbal rules, and standard algebraic notation; (Grades 5 - 8) [2005]
- 1. read and construct displays of data using appropriate techniques (for example, line graphs, circle graphs, scatter plots, box plots, stem-and-leaf plots) and appropriate technology; (Grades 5 - 8) [2005]
- 1. demonstrate meanings for integers, rational numbers, percents, exponents, square roots, and pi (π) use physical materials and technology in problem-solving situations; (Grades 5 - 8) [2005]
- 1. estimate, use, and describe measures of distance, perimeter, area, volume, capacity, weight, mass, and angle comparison; (Grades 5 - 8) [2005]
Colorado Science
- Standard 1: Students understand the processes of scientific investigation and design, conduct, communicate about, and evaluate such investigations. (Grades 0 - 12) [1995]
- Standard 5: Students know and understand interrelationships among science, technology, and human activity and how they can affect the world. (Grades 0 - 12) [1995]
- 2.1 Students know that matter has characteristic properties, which are related to its composition and structure. (Grades 0 - 12) [1995]
- 2.2 Students know that energy appears in different forms, and can move (be transferred) and change (be transformed). (Grades 0 - 12) [1995]

When a skydiver jumps out of an airplane, the force that prevents him/her from accelerating towards the earth in an uncontrolled way is drag. Drag acts in the direction opposite to motion. This opposing force slows down anything moving through the air. You can feel drag if you stick your hand out a car window while the car is moving. It feels like a pressure pushing your hand backwards. The amount of drag that your hand creates depends on factors such as the size of your hand, the speed of the car and the density of the air. If you were to slow down, you would notice that the drag on your hand would decrease. If you change the position of your hand, you can increase or decrease drag by changing the amount of surface area facing the direction of movement.

The drag force generally increases for objects with a large surface area. For example, the large surface of a parachute helps a skydiver create more air resistance. We see many examples of drag reduction when we watch competitions in the Olympics. Championship skiers, speed skaters and bicyclists squeeze down into a tight crouch. By making themselves "smaller," they decrease the drag they create, which allows them to move faster.

Drag exists because of the motion between a fluid (even air!) and an object. It doesn't matter if the object is stationary and the fluid is moving, or if the fluid is still and the object is moving through it. What really matters is the difference in speeds between the object and the fluid. This is why wind tunnels (an enclosed space with a stationary object surrounded by moving air) can be used to study the aerodynamics of objects — the drag forces are the same as if the object was moving and the fluid was still.

Before the Activity

Gather materials.
Choose appropriate locations for students to drop their helicopters.

With the Students

Helicopter Model Instructions (see Attachment, Helicopter Instructions Diagram)

Fold and cut one sheet of paper in half lengthwise.
Take one of the halves and again fold it in half lengthwise.
Use a ruler to draw a triangle along the unfolded edge of the paper. The triangle should start 4 inches from the bottom corner of the paper. It should follow the edge for 2 inches and extend to the middle of the paper.
Cut out the triangle. Be sure to cut through both layers of the paper.
Open the paper and cut down the center of the paper from one edge of the paper to the top of the triangles. See pattern attached.
Fold the tabs toward the center, as shown in the illustration. Use a small piece of tape to secure the tabs.
Fold the wings in opposite directions.
Test the helicopter, to make sure it works.

Helicopter Activity

Have pairs of students work together. Print out two worksheets for each pair. Have each student team create one helicopter from the instructions and predict the times for helicopters to fall and record predictions on the board. Student roles: one student releases the helicopter; a second student times the helicopter's descent and records the time.
As a class, decide a height from which to drop the helicopter. Then, discuss a method for dropping the helicopter. Everyone should use the same method of dropping the helicopter. How can the timer best see when the helicopter hits the floor? Agree on a method for timing and review how to use the stopwatches.
Have students determine where to hold the helicopter to drop it from the agreed-upon height. Each group must determine this position for each member. They should stand on a chair and use a measuring tape to make sure that they are dropping the helicopter from the correct height. Some students may have to hold the helicopter above their head.
Have students drop the helicopter from the agreed-upon height and record the time of landing, in seconds, on their activity worksheet.
Have students repeat step 4 by adding 1, 5 and 10 paperclips to the bottom of the helicopter.
Have students go back to their desks and create their second helicopter, this time making any design change to make their helicopter move SLOWER. Tell them that this is what engineers do when coming up with the perfect design of something ─ they test an original design and modify it in some way.
As they are working on their "new design," brainstorm with them. Ask the students what can we do to influence forces? Do parachutes/helicopters with larger surface areas go faster or slower? (Answer: Slower) Which force is this influencing? (Answer: Drag) What if we add weight? (Answer: It will fall faster.) Could we make a parachute with a large area and a large weight that falls at the same rate as a small area and a small weight? (Answer: Yes)
Have students change roles (from step 1) and repeat steps 3, 4 and 5 with the new helicopter design.
Allow time for pairs to complete worksheets. Revisit predictions on the board and assess accuracy (meaning, do the answers come close to each other?).
Have the class answer the questions provided in the Assessment section.

Class Activity

After the teams finish recording their data and calculating their average values, bring everyone back together into one group.
Have each team write their average values on the board for each trial. As a class, calculate the average time for each trial of the helicopter. Then, make graphs showing the time as a function of the number of paperclips attached to the helicopter.
Using the class graph, have students predict how long it would take the helicopter to fall to the ground with seven paperclips, 15, 20, etc. (Answer: It should fall faster.)

Pre-Activity Assessment

Prediction: Have the students predict the time it will take for helicopters to fall and record predictions on the board.

Activity Embedded Assessment

Worksheet: Have the students record their observations on the activity worksheet; review their answers to gauge their mastery of the subject.

Brainstorming: In small groups, have the students engage in open discussion. Remind students that no idea or suggestion is "silly." All ideas should be respectfully heard.

What can we do to influence forces? Do parachutes/helicopters with larger surface areas go faster or slower? (Answer: Slower)
Which force is this influencing? (Answer: Drag)
What if we add weight? (Answer: It will fall faster.)
Could we make a parachute with a large area and a large weight that falls at the same rate as a small area and a small weight? (Answer: Yes)

Post-Activity Assessment

Question/Answer: Ask the students and discuss as a class:

What is the force that pulls the helicopter/parachute to the ground? (Answer: Weight)
What force is acting in the opposite direction to the force of gravity when you drop the helicopter/parachute? (Answer: Drag)
Which of these forces stayed the same throughout the entire activity? (Answer: Drag)
Why did drag on the helicopter stay the same? (Answer: Because the shape and size of the helicopter stayed the same.)
What happened to the descent time for the helicopter as you added paper clips? (Answer: The descent time decreased as the weight of the helicopter increased.)

Discussion Question: Solicit, integrate and summarize student responses.

Describe how the paper clips affected the landing of the helicopter.

Writing: Have students answer the following questions in a short paragraph.

How could you design your helicopter/parachute to make it more effective?
What do you think your design would accomplish that this helicopter design did not accomplish?
Would your observations for this activity change with your new model helicopter?

Integrated Teaching and Learning Program, College of Engineering, University of Colorado at Boulder Sabre Duren, Ben Heavner, Malinda Schaefer Zarske, Denise Carlson © 2004 by Regents of the University of Colorado.
The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0226322. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.

Last Modified: June 11, 2007