Cutting with Wedges

We got started on science a little late this week, but all of our little projects were a lot of fun, so it was still a good lesson.  We talked about the simple machine called the wedge.  I started out using the same ramp we played with during our discussion of inclined planes last week so that they could have a visual reminder and be able to actually see how the two are related.

Athena read the page on wedges aloud from our mini-book on simple machines, and everyone came up with a few examples of wedges from around the house.  They had a hard time identifying these at the beginning of our discussion, so I pulled our the Usborne Science Encyclopedia to give them a little more information and provide more examples.

Our first demonstration came from Starting with Science: Simple Machines.  I cut some carrot slices and asked the kids to try to push them into an apple with no extra tools.  They made a couple good dents, but weren't able to pierce the skin.

Then I cut the carrot slices into little wedge shapes, and they tried again.

Success!  It took much less effort to push the carrot pieces into the apple when they were shaped like wedges.  And we were able to make some fun goofy faces, too. :)

Then it was time to take a little art break and color papers.  The kids came up with some nice drawings, and it was almost a shame to turn them into paper airplanes at the end.  I used this time to explain how wedges can "cut" through more abstract things, like air and water, as well as literally cutting like a knife.

Our final (and most fun) project was definitely the boats.   The kids were a bit more fascinated with the rubber band motors than the wedge shape that allowed the boats to push through the water with ease, but it was still a good demonstration.  We did try pushing the boats facing forward (wedge in front) and backward (flat front) to compare the effort needed to get them through, but it was tough for the kiddoes to tell the difference.

By the end of the lesson, they were able to find several new examples of wedges around the house and explain for their journals how they do work.  We were able to push through some unclear examples and enjoy a little goofing around and still get the point across.  Next week is our last simple machine before we get to put them all together for some goofy compound machine building for review, so I'm getting pretty excited checking out all the fun we have in store.

--Little Miss Crazy