I picked up a new digital scale today for $12. It has a precision of 0.1 grams and a maximum capacity of 1000 grams. Accuracy is +/- 0.1 grams. I tried to weigh a matchstick rocket, and got a value of 0! So I set up the 10x lever and this time got registered a weight of 0.12 grams. We will need to get an even more precise scale if we are to measure the difference in weight before and after the match head burns off.
Matchstick rockets (we called them pocket rockets) were all the rage when I was in 5th grade. No one I knew then burned anything down or shot out an eye, but this experiment involves matches, and you shouldn't play with matches! So be safe, and do not attempt this experiment unless you are responsible. If you are irresponsible or careless then make sure you have adult supervision (which you will need if you are playing with matches or not!)
NASA actually has a web page on matchstick rockets. See: http://www.grc.nasa.gov/WWW/k-12/TRC/Rockets/match_rocket.html While the NASA site has a lot of good information, it doesn't attempt to quantify or measure anything! So how can make quantitative measurements about matchstick rockets? To make a matchstick rocket, you wrap some aluminum foil around the head of a paper matchstick. Then you ignite the match with heat from either a lighter or another match. A paperclip serves as a launch pad. When the match head ignites, hot gases are quickly formed, and the foil causes these gases to shoot back along the length of the match. Newton's third law states for every reaction there is an equal and opposite reaction. The rocket shoots forward with the same momentum as the gases that shoot back. So how much gas is emitted by a burning match head? At what velocity are these gases shot? How heavy is your matchstick rocket? What velocity does your matchstick rocket achieve? How far will it go? What other forces are at play? Let's find out! |
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