Balloon Brain: Designing a Helmet

Resource for Grades K-8

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Balloon Brain: Designing a Helmet (Document)

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Background Essay

Undoubtedly, one of the most important organs in your body is your brain. It's no accident that adaptations through evolution have completely enclosed our brains in the protective structure of our skull. Thanks to our skulls, falling in the bathtub or bumping into the doorframe is rarely fatal or debilitating -- aside from those moments of extreme pain shortly after impact. And while the skull is tough, it unfortunately doesn't always provide adequate protection for our brains. This is why it's important to always wear a helmet during high-speed activities like bicycling, skating, and skiing, activities in which falling -- and falling fast and hard -- is a very real possibility.

Helmets provide an extra layer of material between our heads and whatever we might crash into. But helmets aren't made of just any material or in any shape that happens to look nice. A pillow tied around your head would provide some protection against small bumps, but it would be nearly useless in the event of a high-speed bike crash. Helmets are designed to provide a much higher level of protection in the event of such violent crashes.

When you bump against anything, your body undergoes a sudden change in speed, from high speed on impact to a complete halt. In lay terms, we say that your body decelerated, or stopped, but scientists use the term acceleration to refer to any change in speed. Helmets protect by extending the period of time it takes for your head to accelerate. This acceleration may take only 1/100 of a second in an impact without a helmet. A helmet, however, extends this time to 7/100 or 8/100 of a second. By lengthening the period of acceleration, the helmet reduces the force applied to your head at any given moment. A rigid and well-fitting helmet also distributes the force around the helmet structure so that less of the total force focuses on the point of impact. Lastly, the slick surface of a helmet slides more easily across the road or ground than a bare head does, further lengthening the period of acceleration. These features may not sound like much, but they can make the difference between life and death or brain injury.

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Discussion Questions

Bubble wrap and egg cartons are two of the materials used to solve the problem of protecting the water balloons. Describe the properties of each material that make it a good choice. Are there any downsides to using either one? What other materials would you use? Why?

Did you notice how the water balloons came to a complete stop very suddenly when they hit the wall and then the floor? How did the homemade helmets protect the balloons at the moment of impact?

Take a look at some bike helmets. In addition to the materials that make up a bike helmet, what other criteria do you think designers take into consideration?

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Transcript

(electricity crackling)

CAROLINE: This is Chubby Brain.

ESTUARDO: And this is Pudge Brain.

GARRETT: Since they're water balloons, these brains, like our own brains, are pretty delicate. So our challenge today is to build a skull to protect them.

ALINE: Stephanie C. of Katy, Texas, did this experiment at school to learn how our skulls protect our brains. We're allowed to use any of these materials, but our skulls can't be more than two to three inches thick, and they can't cover the faces of our balloons.

CAROLINE: Later, Kortney will test out our designs by throwing them against this wall and seeing if they survive. Okay, guys, let's test it out.

ESTUARDO and ALINE: Okay.

CAROLINE: All right, so I think what we should probably do first is maybe layer the balloon with cotton balls just for protection.

ESTUARDO: I think we should do soft right here on the... and then we should keep on working up to thicker stuff.

GARRETT: What if we, like, cut an egg carton? You see these, like, bottom...?

CAROLINE: Yeah.

GARRETT: What if we, like, cut those off...

CAROLINE: Oh!

GARRETT: …and stuck them to it? Then stick it on around it.

CAROLINE: That is such a good idea.

GARRETT: Then it will hit this, and even less damage will be inflicted.

CAROLINE: Awesome— high five— that's awesome.

ALINE: Okay. Oh, he's wicked heavy.

ESTUARDO: We really need to make it tight so he has no chance of falling.

CAROLINE: He's so cute.

ALINE: Are you guys done?

CAROLINE and GARRETT: Yep.

ESTUARDO: Let's test them out.

ALINE: Let's go. Okay, ready? Ready, ready, ready?

CAROLINE: Let's back up, then.

ESTUARDO: I'm scared.

GARRETT: Ready?

CAROLINE: Chubby!

ALL: One, two, three.

CAROLINE: (shrieks)

GARRETT: It survived! It survived!

CAROLINE: Oh, Chubby!

GARRETT: Oh, Chubby! Ready? Oh, my...

ALL: One, two, three.

GARRETT: Oh, man!

ESTUARDO: No...!

ALL: (laughing)

GARRETT: Oh, little Chubby! (pretending to cry)

CAROLINE: Our balloon brain survived, because it stopped gradually as it hit the wall. The cotton balls that were directly next to the balloon helped slow it down, and the egg crates around the balloon helped to distribute the force around the whole balloon so that the force of the hit wasn't on just one area of the balloon. These two things helped make the force on the balloon much smaller when it hit the wall, so the balloon didn't break.

ALINE: Our balloons broke because our faces weren't padded. Without this protection, the force from the floor that stopped the balloon also broke it.

ALL: (exclaiming)

GARRETT: Bicycle helmets are engineered to do the same thing as skulls we build for the water balloons. They give extra protection to our head. The foam inside a bicycle helmet slows your head down and prevents it from colliding suddenly, and that means less force on your head.

CAROLINE: The stiff outer shell distributes the force throughout the helmet, so each part on your head takes a little bit of the force, instead of having a lot of force on just one spot. This is why it's so important to wear a helmet when you ride a bike.

ESTUARDO: Experiment with the balloon brains at your home and see if yours can survive more throws than ours did.