How can I explain Newton's third law (that for every action there's an equal and opposite reaction) in a simple demonstration?
We recommend using the search engine dogpile to find some good websites. Dogpile searches using 'natural language' so you can just type your question into the search box.
HOT TIP: Dogpile suggests other possible searches to try under Are you looking for? (on the right hand side of the page). Sometimes this is great for narrowing down or expanding your topic if you are not finding what you want. When looking at your results list, try to avoid the links which say "sponsored link". These are usually trying to make money or sell you something. They may have some useful info, but try other websites first.
Try the keywords demonstrate Newton's third law. There are lots of options but we quite liked Swift's Newton's 3rd law site.
One of the sites we often use for science-type questions is How Stuff Works - and they have a whole section on Newton's laws.
HOT TIP: Check out our ManyAnswers entry on Science Fair Projects for more great links!