How can we make sand stand tall?
What does "stable" mean?
Where is the center of gravity and center of lift of an airplane?
How does the airplane's tail (horizontal stabilizer) keep the airplane stable?
Explain why the position of the centers of gravity and lift is important.
Be able to find the correct position and amount of extra weight to make a glider fly well.
Weight and balance
Based on learned knowledge, locating the weight balance location in an airplane
Weight and Balance
Small-group Hands-on Scientific Inquiry (15-20 minutes)
Finish last activity if needed
Explain that for any object (including an airplane) there is a point where the weight is centered and gravity seems to act at this one point for the whole object. This is called the object’s center of gravity.
10-minute activity: Invite students to find the center of mass of classroom objects (pencils, rulers, etc) by finding the point where the object balances.
Regroup and say, "airplanes have a center of gravity and also a center of lift which is the same idea, but the center of lift - it’s the point where lift pushes up on the airplane."
Center of Lift
Center of Gravity
Give each group a foam strip, paper clip, and a binder clip.
Attach the paper clip on one end to represent the balancing tail load.
Tell them they can only push up on the strip at the center (representing the center of lift).
Tell them to find where the binder clip needs to go to add extra weight so they can most easily balance the strip while touching it only in the middle.
Discuss as a group where the binder clip had to go (students should find that they have the most control if the binder clip is slightly in front of the center of lift as shown in the diagram).
Explain that an airplane is stable if it is easy to control using the tail surface.
Small-group Hands-on Scientific Inquiry (30-35 minutes)
Use the foam gliders from last week. Review first: We added weight to the airplane to move the center of gravity so the airplane flew well.
Tell students their task is to gently bend the back end of the tail (horizontal section) up and the front down. Ask the students what this will do to the airplane performance. Create a hypothesis.
Provide the Weight and Balance Flight Record Sheet for students to use to collect their data. NASA activity page 59 from last week's lesson
If desired, discuss as a group what data to collect before they start. Some possibilities are:
How far did it go?
How long did it stay in the air?
Did it go up or down?
Did it fly straight?
From your judgment, did it fly well?
Test the airplanes again. Add paper clips if needed. Note changes in performance.
After testing discuss the results as a group use the following discussion questions:
How could you tell when the glider was stable?
When the glider is stable how is the center of gravity compared to the center of lift? How do you know?
What did changing the tail do? (creates more balancing tail load and you need more weight to counter it)
End of Session Reflection and Debriefing
Teacher briefly explains the computational thinking (CT) skill embedded in the Problem Solving Process Diagram. Using the problem solving process diagram, the teacher will ask students to identify what kind of problem solving skills/process/computational thinking they used in this session and explain how they used it. The following are some sample questions that can guide the debrief.
What did I learn today?
What problem solving skills/processes or CT components in this diagram did I use today?
How did I use the problem solving skills/processes/CT components?