Try out this easy DIY science experiment at home. All you need is a balloon, a penny, and a hex nut. Place the penny or hex nut in the balloon, blow it up and then tie it off. It’s as simple at that! Now give your balloon a good spin and make some observations. Try using many of your senses for this one, but maybe avoid tasting it.
The penny races around and around with little sound, and it takes a really long time to stop spinning. This is due to something called the centripetal force and the conservation of momentum. Centripetal force is the force that makes something continue spinning if it is already in a circular path. It is a force that constantly pulls an object towards the center of its path. Newton’s first law states that an object in motion tends to stay in motion and an object at rest tends to stay at rest unless acted upon by an outside force. In the case of the penny that is constantly spinning in the inside of the balloon, it wants to continue moving. However, if the centripetal force did not exist then the penny would want to travel in a straight line and slam into the inside of the balloon, causing it to come to a crashing halt of motion.
The hex nut also has a centripetal force on it, however the biggest difference between it and the penny is that the hex nut makes a ton of noise. The noise actually comes from the fact the the hex nut has sides. Those sides attribute to more friction which causes vibrations on the balloon. Those vibrations are turned into sound waves, which is the noise that you here. What do you notice as you increase or decrease the rate of rotation of the hex nut? You should be able to notice a definite difference in volume level as well as pitch. If you spin it faster it should get much louder and at a higher pitch. This is also true for other things like vocal chords. The faster that you pass air along them, the higher the pitch will get. What other things can you think of to put inside of your screaming balloon? What differences can you observe?