i need two scientific demonstrations?
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google any science homework help site, there are good ones.  also check out wikipedia
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Try this site the demo is very good http://www.byki.com/
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look in a library book or a science book...
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What equipment?\nWhat experiment?\nWhat error?
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These two pages might help. Scroll down on the first link for what I think you're after.
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Try Lancaster Synthesis.
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Here's an interesting experiment.
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http://www.pa.msu.edu/sciencet/ask_st/111192.html
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Yes, you need a lab to do this! If that wasn't clear to you, this may not be the best project to try to copy!\n\nWhy not have an idea of you own, something you can do with what you have at hand at home? You might learn something!
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Walk over to the science lab and ask one of the professors, or if you are a middle school student, ask one of the teachers.  I am assuming this is for a legal purpose of course.
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I'm guessing the project needs to be an experiment and not just a demonstration.\n\nWhat area of science are you expected to work in? Are you allowed to use live subjects? \n\nPhysics:\nHow does the length of a string affect the period of a pendulum?\nHow does the density of a material affect the speed of sound?\n\nBiology:\nHow does the color of a light affect the growth of a plant?\nHow does caffeine affect a rat's ability to learn?\n\nAnother thing you might do is Google science projects or go to the library and look for a book.
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THE EASIEST WAY TO DEMONSTRATE GENERATION OF ELECTRICITY IS TO GET SOME SMALL INSULATED COPPER WIRE AND WRAP IT AROUND A SMALL PILL BOTTLE,  AT LEAST 100 TURNS OR MORE (MORE IS BETTER) CLEAN THE INSULATION OFF THE ENDS OF THE WORE AND ATTATCH TO A VOLTMETER OR A MILLIAMETER.. INSERT A BAR MAGNET INTO THE PILL BOTTLE QUICKLY.  THE METER WILL GO ONE WAY WHEN YOU INSERT THE MAGNET AND WILL GO THE OTHER WAY WHEN YOU PULL THE MAGNET OUT.  THE FASTER YOU MOVE THE MAGNET THE MORE THE METER MOVEMENT.  HOPE THIS HELPS
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I suggest this one : http://www.all-science-fair-projects.com/
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http://www.lancasterlabs.com/  try that
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http://www.aapt.org/Events/physicsday.cfm\n\nThere you go!
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Do the experiment.  You might learn something.
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Search at these sites.  It can be done, but it is usually not economical.\n\nhttp://www.scirus.com/srsapp/\n\nhttp://www.scienceresearch.com/search/