At this point, when I say, "Simple machines trade distance for effort." I expect eye rolls. How could you not? It's been repeated an estimated 103,000 times since we began the unit. And I smile just little a bit every time you roll your eyes because that's the same reaction I have every time I'm forced to sit through something I already know.
We're nearing the end of our simple machines unit and in preparation of the test, here's a round up of what we've explored along with resources to make sure you're ready. Keep an eye out for purple links in the text to video and interactive resources.
Exploring the Key Concepts
The Inclined Plane
We began with a box of books. The challenge was to move the box onto the table. The first group had fewer members but could take the books out of the box, the second group could not. The first group got to work, hurriedly stacking the box's contents on the table. Using only two fingers, the second group pooled their human resources and in one fell swoop, heaved the box skyward.
The first group saw that they had traveled more distance in accomplishing their goal while the latter group used more effort. But what if the box's contents was solid? The first group would be at a disadvantage. We needed a way to get our distance back. The solution: an inclined plane.
Levers
This unit was a balancing act right from the start. Literally. Our first investigation asked students to use a yard stick and a crate as the fulcrum to balance out a cup of cubes. Students discovered how changing the distance of a lever's arm affects the amount of effort needed to lift a load of 15 cubes. The first model they constructed placed the fulcrum in the middle of the lever creating an equal distance between the effort and load.
The second diagram placed the fulcrum further from the load. Students discovered that it takes a lot more work (force x distance) to lift the load. I have to say, it was a blast to watch them patiently counting out the cubes waiting expectantly for the load to budge. They'd run out of cubes around 40 and have to scramble around to borrow from the other groups right in the middle of the test.
When it came to the final test, the students thought they were doing something wrong.
Many groups came running, "What are we supposed to do." After a few questions, the lightbulb would go off, ohh we don't have to do anything, the load is already lifted.
I hope students walked away with the understanding that it's a pain to do extra work (not school work, that's different mind you). You have to run around asking to borrow cubes and picking stray ones out from underneath the heater. When you use simple machines to your advantage, you let the machine do the work.
Then, we put this information to work. Armed with a marker and popsicle stick students to part in the First Annual Flip Off. The objective, use your knowledge of levers to flip your cube onto the colored tiles. Every time you land the tile you move your lever back a square. Some students used less effort the closer they were and some positioned the fulcrum so their cube gained more hight. And some students launched their cubes up into the lights, which incidentally, I can't quite admonish you for as I surely would have been that student. To conclude, students reflected on how they used their knowledge of levers, distance, and effort to land the cube.
Wheel and Axle
Sure, it was entertaining to see the kids reaction upon walking into class before the wheel and axel demonstration. But it was even more entertaining to see their response to my explanation, "You act like you've never seen a couple bicycles hanging in the front of a classroom."
We started with the bike in a lower gear and measured the distance the wheel traveled in one pedal rotation. After shifting into a higher gear, we measured again. Students saw that in order to cover the same ground, the pedal needed to travel a greater distance in the form of more rotations.
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| Image Credit: Jamie Anderson |
The Wedge
Next Week In Science
Monday: Wedge Activity: Collecting and recording data to draw conclusions
Tuesday: 6 categories of simple machines study guide: Note-taking from video and interactive media
Thursday: Wrap up and review: Revisit KWL (what we think we know, what we want to know, what we've learned) chart
Friday: Assessment
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