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Kevin and the rest of the folks from the TheBackyardScientist decided to ask what happens when you put 20,000 Joules of Energy into a watermelon and other things. Why? Why not? Is it science? Is it art? Who cares (except the neighbors who threatened to call the cops on them)? It’s cool, Dude! Watch their video and also learn about capacitors.
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If two grenades fall near you, one on the ground and another in the water, what would you do? Would you dive in the water a certain distance away from the underwater grenade hoping that the water will shield you from the shrapnel, or would you dive to the ground hoping that not a lot of the shrapnel from the surface blast would hit you? Mark Rober teams up with Kevin (TheBackyardScientist) to figure this out. Their video is very good, so I will leave the explanation of the science up to them, but you can also check a written version here. I have posted in this blog about how the chemical and physical characteristics of an element can be dramatically altered by other elements with which it combines. A case in point is sodium chloride (table salt), which is an innocuous chemical. However, as the video from the BackyardScientist below demonstrates, molten sodium chloride can be quite explosive when added to water. However, this reaction seems to be a physical reaction not related to the explosive properties of elemental sodium. It may have to do with the way the water is heated and converted to vapor very fast within the blob of the molten salt as it goes under the surface of the water. 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. 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. |
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