Simple Machines: Inclined Planes

Studying Simple Machines is one of those things every child has to do at some point, so there are tons of books, tons of lesson plans, and tons of other resources on how to teach about them. I don't think we did anything that extraordinary, but we had fun anyway. We spent a day on each type of machine, so I'll just show a few of the activities we did, most of which were suggested by books we read or lesson plans we found online.

Inclined Planes are a good place to start, since they're so basic, and they are one of the two larger categories that simple machines fall into. (The other being Levers.) We did some basic demonstrations, like dropping a hard boiled egg from a certain height and observing the force with which the egg hits the ground:

(a lot)

And then trying to find ways to reduce the force, using inclined planes. We managed to get some mostly uncracked eggs by rolling them down longer and longer ramps. It was a good way to illustrate the concept of trading force for distance.

We also measured force using a simple homemade spring scale (something like this).

We could see how a weight pulling straight down on the scale exerted a lot more force than a weight partially supported by an inclined plane.

Our favorite video explanation of inclined planes was this one. It's from a whole series on simple machines, but for convenience I'll link each machine's video on the corresponding blog post here.

Another thing I think would be fun to do for an inclined plane study is make a marble run out of toilet paper tubes and popsicle sticks, something like this. We have some marble run blocks, but it would be fun to experiment with how different angles of inclined plane allow the marble to reach different speeds, and how that affects the force and distance the marble achieves within the system.

This is a great lesson plan for learning about inclined planes. It also contains a good review/overview of forces and work, as those terms are used in physics.

If you want even more of a review, you can watch this video on friction and mechanical advantage—

and this one on work—

and this one on Newton's laws of motion.

Hydropowered "Generator"

Well, frankly, this was a little disappointing. When I was preparing to teach about hydropower and generators, Sam said, "Why don't you build a generator?" I didn't think I could handle helping the boys do that by myself (I'm just barely learning how they work myself!), but the more I thought about it, the more I thought the boys would get really into that idea, so I finally found some instructions that seemed detailed enough for even me to follow. They had pictures and a supply list and everything. The hardest part was finding copper magnet wire, which the instructions acted like could just be picked up at any old store. Home Depot and Lowe's didn't have any of this gauge (very small---24), and neither did Radio Shack, where they sent me. I finally ordered it from Amazon, which I should have done in the first place.

The rest of the supplies were mostly things we already had, or fairly easy to come by, so we set aside an afternoon to work on it. Seb and Abe (the only ones I really thought could participate) were SO excited. We wound and wound and wound until we had four coils of wire. But then things started to be complicated. We didn't have quite the right size cork, or quite the right size dowel, and we tried to make it work but we weren't sure if it was going to. And our current, when we tested it, was definitely doing something . . . but we couldn't quite tell if it was doing what it was supposed to do.

Anyway, the long and the short of it is, the turbine turned beautifully (with enough water pressure, e.g. the hose) but we couldn't tell if it was actually generating any power for us or not. The tiny flashlight bulb we tried to hook up didn't light, but we weren't sure if that bulb would even work with alternating current, and then our multi-meter didn't get consistent readings, but we don't know if that's because we didn't have good contact with the wires (hard to hold it still when you're trying to hold the hose on the turbines) or because the current wasn't running. There were just too many variables. Was the incorrect dowel size causing trouble? We couldn't see why it would be, but who knows? Did it matter that I put the turbine in the bottle upside down (yes, that was my stupid mistake) so we were sending in the water from the bottom instead of the top? I just don't know enough to decide what matters and what doesn't.

After spending so much time building the thing, we were quite sad not to know if was actually working or not! However, the upsides were: 

• it was cool making the turbine spin---the boys loved that, and it was impressively fast and powerful (better than our paper cup waterwheels).
• it was pretty fun to build---we liked wrapping wire and cutting spoons and so forth
• we really got a solid understanding of the parts of a generator. You always remember things better when you've handled them and worked with them; so now, for example, the boys don't forget which part is the stator and which is the rotor, or which part has the magnets, or why the turbine has to be attached to a shaft that turns the rotor, etc. I feel like I truly grasped those concepts for the first time as we were making it.

So I wouldn't say it was a waste of time, and I do think it was probably our mistakes that caused us to go wrong, not the instructions---they were pretty clear. (Though perhaps they could have been slightly clearer . . . ) This is a project we may attempt again later, when I've recovered from this time. :)

Waterpark Field Trip, and How Water Slides Work

On the childrens' birthdays, we have a tradition of doing something fun together as a family. (We usually only give 1-2 gifts, so their activity is sort of their gift as well.) For Daisy's birthday we went to the Aquarium and for Seb's, we went to a waterpark. Now this sounds like one of those "mostly-just-fun-thing-trying-to-justify-itself-as-'educational'" types of Field Trips---and I would have been totally fine with that, since this was actually a birthday activity, after all---but surprisingly, the lesson leading up to this Field Trip was one of the most interesting and informative of the whole unit, I thought. We had a library book on "how water parks are built," but I thought the most useful resource we used was this website. It has diagrams of the parts of a water park system (the pumps and filters that keep the water moving), explanations of kinetic and potential energy, and more. It was awesome. From this same site, we learned about "water coasters" (we'd never heard of those!) which use strong currents or magnets to push you UP hills as well as down---like a roller coaster in the water. We looked up a bunch of videos so we could see those in action. (e.g. here)

Seeing how these concepts are applied in real life added substance to our discussion of inertia, friction, thrust and drag, types of energy, etc. And it was great to see the children running around at the water park calling out things like, "Look Mommy! Cantilevers!" and "Whoa, did you see the way my inertia pulled me up the side of that curve?"

Also, we just had a fun time. :)

I'm cold.

Splash!