We were very ambitious indeed for our program on 2/9/12. Using several demonstrations and experiments with balloons, our G3 scientists learned about:
- The Properties of Polymers
- Centripetal Force
- Newton’s 3rd Law of Motion
We started the program with a quick discussion about the properties of polymers. In particular, how the rubber in balloons is made of long strands of molecules called polymers. And it is the elastic quality of the polymers that allows the balloon rubber to stretch. Nicole then wowed the room with a demonstration she learned from Steve Spangler’s web site: The Balloon Skewer. By coating a standard bamboo skewer with vegetable oil (for lubricant), you can push the skewer in one side of the balloon and out the other side…without popping it!
[The trick is making sure the entry/exit points are where the balloon’s rubber is LEAST stressed, or more opaque looking then the rest of the balloon – near the base where you tied off the balloon, and at the opposite end and top point of the balloon.]
Each G3 scientist was given a clear balloon and a skewer to try their hands at this demonstration. The vast majority were a success…though the sounds of popping balloons could be heard here and there throughout the room. Practice makes perfect 🙂
Our conversation then turned to centripetal force. The word “centripetal” is actually Latin for “center seeking.” And that truly describes this force. Without centripetal force, objects would not be able to travel in a circular path (they would only be able to travel in a straight path). One example Nicole offered the G3 crew was a satellite orbiting the earth. In this case, the centripetal force is supplied by earth’s gravity (think of it like an invisible thread that links the earth to the satellite and keeps the satellite moving around the earth in a circular orbit). Another example is the swings ride at an amusement park, where the centripetal force is supplied by the chains that link the chairs to the central pole. A couple of videos also demonstrated this principle perfectly. One video was a demonstration provided by Jeff Williams on the International Space Station (ISS). He showed how, due to centripetal force, the bubbles in his iced tea package would move to the center of the package and form a large, singular air bubble when the package was put into a circular path. The other video showed a “death cage” motorcycle demonstration at the Barnum & Bailey circus!
Yet again, our G3 scientists turned to balloons for help in understanding another scientific principle. First, we all attempted The Spinning Penny as described on the Steve Spangler web site. A single penny is placed inside a clear balloon. The balloon is blown up and tied off with the penny still inside. After shaking the penny a bit, the balloon is then swirled to help start the penny on a circular path inside the balloon itself. Due to the limited amount of friction, the penny can stay on its circular path for close to 30 seconds before gravity begins to slow it’s path! Our scientists all managed to create this very cool demonstration of centripetal force. We then did a twist on this demonstration to create what Steve Spangler calls “the screaming balloon.” We replaced the penny with a zinc hex nut…and guess what? The nut also moves on a circular path within the balloon due to the centripetal force we supply, but there is more friction between the hex nut and the balloon thanks to the the shape of the nut, and thus we get a high-pitched whining sound! Very fun for us…maybe not so fun for friends and family 🙂
While we all had fun with the demonstrations, it was now time for some actual experimentation. Nicole introduced our G3 crew to Sir Isaac Newton’s 3rd Law of Motion: For every action, there is an equal and opposite reaction. To test this principle, we followed the guidelines of Science Bob to create our very own balloon rockets. Nicole had our scientists break into teams of 2, and each group found a pair of chairs with some kite string strung between them (like a zip line). A straw was threaded onto each string. Nicole provided balloons of varying sizes for the scientists to blow up, tape to the straw, and release. The result mimics the take-off of a rocket, with the air pushing back in one direction and propelling the balloon in the opposite direction. The straws were different lengths, and there were 3 different sizes of balloons to experiment with. [While the really long balloons were popular, they sure were difficult to blow up!]
At the end of our hour, every scientist was able to bring a copy of these simple demonstrations and experiments home with them, along with an activity sheet to help continue the learning. I wonder what Nicole has planned for our scientists next!…