Exploding WatermelonRead Now
One of my Twitter followers named Ken has a You Tube Channel called Kid’s Fun Science where he posts the science experiments that he conducts during Science Night at his local Elementary School. In the video below he shows the blowing up of a watermelon employing rubber bands using the potential energy accumulated in rubber bands after stretching them around the melon.
There are several forms of potential energy. The potential energy stored in an stretched rubber band is called elastic potential energy. This type of potential energy can be stored in elastic materials as a result of stretching or compressing and can be converted very rapidly into kinetic energy (energy of movement) when the force opposing the compression or stretching (in this case the structural integrity of the watermelon) is eliminated. Check out at the end of the video the final fate of the rubber bands after the release of their pent-up energy!
I encourage you to check other fun science experiments in the Kid's Fun Science You Tube Channel and to follow them on Twitter, Facebook, Instagram, and Pinterest.
Dry Ice BombsRead Now
This is a favorite of kids and teenagers: dry ice bombs. Put some dry ice in a plastic bottle filled with water, screw the lid tight, and run away. The dry ice sublimates producing carbon dioxide gas. One kilogram of dry ice can produce about 16 cubic feet of gas, which is quite a large volume expansion. The gas produced inside the bottles leads to a pressure buildup that produces its explosive rupture.
Filming these explosions underwater with high-speed cameras has produced some amazing footage that illustrates scientific principles regarding pressure waves and how they travel through water and air.
However, making these bombs is very hazardous. Not only can they explode unpredictably, but the very loud sound from the explosions can cause hearing loss, and pieces of shrapnel from the bottle or small pieces of leftover dry ice can damage the skin or eyes. Over the years many injuries have been reported in the United States as a result of both accidental and intended detonations of dry ice bombs, and it is illegal to make these devices in several states.
Have you ever wondered what would happen if you shoot a ball from a truck travelling in the opposite direction in such a way that the speed of the truck matches the speed of the ball? That is what the Mythbuster folks did in this video.
Fun with AcousticsRead Now
In the video below Physics Girl uses a vibrating plate and sand to create cool patterns called Chladni Figures, named after the German physicist Ernst Chladni who studied these patterns in the 18th century.