# Sky floater hands-on challenge: explore buoyancy and air pressure with PBS's Design Squad Nation.

The "hover" test! The Sky Floater activity from Design Squad[TM] Nation challenges kids to make a balloon hover in one spot and then use air pressure to drive their balloon.

Bring the engineering concepts to life with resources from Design Squad Nation's online educator's library. In addition to the hands-on activity, there's an animation explaining buoyancy, a TV episode about remote-controlled blimps, and a video profile of engineers who operate some of the world's largest blimps. Everything you need to lead Sky Floater is in the Parents, Educators, and Engineers section of the website's Force/Energy topic area. Find it at pbskidsgo.org/designsquadnation/parentseducators.

Identify the Problem

Give kids their challenge: Make a helium-filled balloon hover in one spot, and then move it around the room without touching it. They'll use helium-filled mylar balloons, paper clips, and cardboard.

Show the How Does a Blimp Float? animation, which describes how a helium-filled balloon floats. Ask: What are the forces affecting your balloon? (Gravity and lift) What do you know about these two forces when a balloon is neutrally buoyant (i.e., when it hovers)? (The force of gravity equals the force of lift.) Why do the balloons rise? (Air is denser than helium--it has more particles per unit volume than helium does. The denser air pushes the less-dense helium aside, producing an upward force called a buoyant force. In our testing, kids called air a "bully.") How is neutral buoyancy an example of Newton's 1st Law? (If the forces of lift and gravity are equal and opposite, the balloon won't rise or fall.) When will the balloon stop rising? (When it hits the ceiling or rises to a point where the density of the air outside the balloon equals the density of the helium inside the balloon. When these two densities are equal, there is no longer a buoyant force.)

Brainstorm and Design

Get students to think about how they can make their balloon hover. Have them test different ways to weigh the balloon to make it neutrally buyoant (so that it floats in the same place for five seconds). Then give kids a "driving lesson." Borrow a neutrally buoyant balloon from one of your students. Ask the class to predict: How will this balloon move when I fan a piece of cardboard next to the balloon but not at it? Demonstrate by taking a square of cardboard and sharply sweeping it alongside the balloon in one swift motion (i.e., no fanning back and forth). Surprise! The balloon moves unexpectedly toward where you swept the cardboard. Repeat on the other side, and above and below the balloon.

Explain that the balloon is surrounded by air. When you sweep the cardboard beside the balloon, you temporarily remove some of the air, producing an area with fewer air molecules (i.e., lower pressure). Surrounding air molecules rush in to equalize the pressure, carrying the balloon with them. By creating a succession of low-pressure air pockets, kids can move the balloons around the room a few inches at a time. End by demonstrating that rapid fanning at a balloon makes it hard to control the balloon's movement. Fanning results in chaotic air currents. They will move a balloon, but in an unpredictable way.

Build and Test

Have kids explore air pressure by moving their balloon around the room. Then tell them to take on the challenges described in the student handout. For example, challenge them to move their balloons in a circle around their partners. Then have them steer the balloon up and over an object, such as a table or their partner's head.

Evaluate and Redesign

Race time! Have teams steer their balloons over a desk and into the seat of a chair. What's the most effective way to move a balloon and win the race?

Share

Have students present their "balloon-driving" techniques. Show the Band Cam TV episode in which teams design and build a remote-controlled aerial camera system to film a live concert. Ask your students what ideas they have for new inventions that use blimps. Have them share their ideas, and check out other kids' ideas, at the Share section of the Design Squad Nation website.

Blimps and Buoyancy: A Real-World Connection

Buoyancy is the force that keeps blimps aloft. Mark Caylao, Head Engineer for Airship Management Services in North Carolina, maintains and operates some of the world's largest blimps for everyone from presidential candidates to the military--for things like research, surveillance, and security. Share his video profile, Blimps, with your students.

Design Squad Nation Takes Flight in Flugtag Competition

Design Squad Nation takes one giant leap when Judy and Adam invite Felipe--an accomplished 15-year-old pilot from Miami, Florida--to help their dreams come true by competing in the 2010 Red Bull Flugtag competition. Guided by expert advice from Felipe and NASA, Judy and Adam design and build a human-powered flying machine. Their NASA-inspired glider soars off a 30-foot high deck, impressing the judges with distance and style. Watch the full episode online at pbskidsgo.org/designsquadnation.

For ideas on how to use this episode as a teaching tool, go to http://pbskids.org/designsquad/parentseducators/ blog/2011/04/one-giant-leap-and-a-pretty-big-splash.html.

More on Buoyancy

Extend your student's learning with more hands-on challenges. Look for these activities that let kids further explore the topic of buoyancy:

* Sky Glider. Use two helium-filled balloons to build a blimp that can travel across the room.

* Blimp Jet. Add a jet-propulsion system (i.e., a balloon) to a Sky Glider blimp so it flies under its own power.

Sky Floater corresponds to ITEEA's STL Content Standards 1, 2, 3, 8, 9, 10, 11 and 16.

Chris Randall, an instructional designer with WGBH's Education Department, develops activity guides, websites, and professional-development resources for WGBH's science and engineering TV shows.
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