Screws versus Bolts

This week we are taking a closer look at one of the six simple machines - the screw. Screws are useful simple machines in that they help us hold things together by applying force through the item or items. They can also take a force that goes around and make it go up and down instead. One of the earliest versions of a screw was invented by Archimedes and used to move water to higher levels in ancient times. Other examples of a screw beyond the kind used to hold materials together are springs, cork screws, and slinkies because they have a spiraling inclined plane wrapped around a central (or imaginary) core. Screws can also be found in nature, especially in shells and shelled animals.

Primary students are comparing screws to bolts using large screws and bolts I found (purchased) at Lowe's, and creating Venn diagrams to help them compare and contrast the two "screws". We have been talking about the ease of installing a screw into a wall because of the wedge on the end whereas a bolt would need to have a hole drilled first. Screws also have their threads (inclined plane) spread wider apart that helps to cut threads into the inside of the hole it is being screwed into; while the threads on a bolt are more standard (to fit nuts on them) and are closer together than on a screw.

The students are able to see how the threads are really one long inclined plane wrapped around and around by taking a paper cut into a right triangle, coloring the angled edge, and then winding it back around itself to make a paper screw.

Fourth and fifth grade students are exploring screws using K'Nex as they construct a hand drill and comparing a drill bit to a screw. They are also learning the mechanical advantages of a screw and how they can calculate the mechanical advantage (MA) by taking length of the spiral and dividing it by the length of the body of the screw (or drill bit, in this case).

For more information on screws as a simple machine, check out these sites:

• Dirtmeister: Screws
• Simple Machines for Kids: Screw
• Examples of Screws
• How is a screw like an inclined plane?

The Search for Simple Machines

This week marks the start of our Simple Machines unit. When we think of machines, quite often we think of some elaborate object with button or knobs that is powered by electricity in some way, either by battery or by a plug in the wall. However, simple machines are the simplest part of a machine, often made of one or very few moving parts. These simple machines make work easier for us by distributing the mass over a gradual slope, lifting items, splitting materials, applying force, or even changing the direction of the force and giving us a mechanical advantage. There are six simple machines: inclined plane, screw, wedge, pulley, wheel and axle, and lever.

As part of getting acquainted with the six simple machines this week, we will be scouring our school looking for and identifying each of the simple machines and talking about how they make tasks easier for us. Students are having to find at least two example of each of the simple machines around our school. (Kindergarten students love going by the flag pole and pointing out the pulley. :) Parents can challenge their students at home to locate examples of the six simple machines at home.

EDP - final week!

Its definitely the final week on our Engineering Design Process unit, and what a unit its been! The next time I do this unit, I will be putting more caps on the amount of time we spend on different parts. This is somewhat difficult to do with our short classes, but one I think we can manage. For starters, I've changed up the reviews for more student interaction and have been using more Kagan structures, such as paired sharing. Its taken a bit to get the students accustomed to the structures, but I think it will help all students in the classroom become more involved in their own learning.

This week the students are writing a reflection piece about how they worked together as a team to accomplish their products, reflecting on the highlights, what went well, what could have gone better, and what changes they would make as far as working as a team the next time.

I have one second grade team that has been trying to finish their project - they got a late start in that it took them several weeks in the beginning to decide on what they were going to make, but I think now they have gotten most of it together, they don't really want to stop. They were so excited and pleased with themselves when they finally figured out they could add other items to their drinking straw that they drew out of the bag originally, and decided to make a garden using straws as slats in fence surrounding the garden. They also could not decide who was going to take it home, so they have decided diplomatically that they would each take it home for a week and add to the garden with paper flower cut outs and toothpick stems. They needed some help with the hot glue adding the straws and wooden craft stick posts on, but the rest they each tenderly worked on as if it were their own garden.

Wooden craft stick fence posts hold plastic straw fencing that
surrounds this garden of green felt grass and construction paper.
Plastic trees from a cake topper were found for the trees, with
miniature pompom bushes, and a pipe cleaner flower. On the back
side is another flower cut from sheer printed ribbon with a straw stem.

Crazy scheduling is coming up next week with Dr. Martin Luther King Day on Monday and Record's day on Friday, with a zero Fine Arts day on Wednesday as we meet together with all of the classes, leaving just Tuesday and Thursday for classes. But, I keep telling the kids that the fun part of STEM, the really fun part, that is, is just around the corner! (Legos, K'Nex, and more!)

Kindergarten is taking a look at screws this week and comparing them to bolts, which are also screws in simple machines terms. I find it interesting how enthusiastic they can get over holding the real things and being able to see the differences between the two themselves. We've also compared a jar lid to a screw and talked about how the lid was like the inside of a hole for the screw, in that it has threads, just like when a screw goes into a hole and cuts threads.