simple machines

[mountain mama]

My boy (3rd grader) has to do a science fair project on simple machines. Seeing as I am an English teacher, I was hoping to get some input from y'all. I was thinking possibly something survival related. Any ideas?

[2dumb2kwit]

How about a very simple tool. The lever.

Maybe a see-saw, with a movable pivot point, to play with lever ratios.

[Old Professor]

He could also demonstrate a screw with a screw jack or a pulley with a small deer hoist.

[BENESSE]

A few ideas:
http://www.ehow.com/info-tip_8068018...-machines.html

[intothenew]

Knee jerk answer;

A wedge to split wood would be a simple one.

An elaborate one could be a well draw.

[BENESSE]

A noose?
2D made me think of it.

[intothenew]

This may be the break I was looking for. Rick's gone for a few, you tie up 2D, we make the project as Old Professor suggests, and I'll cook up the mule.

[crashdive123]

Ken would be so proud.

[2dumb2kwit]

This thread is getting ready to go waaaay off track.

But I'm not going to be the one to take it there.
Nope...not going to do it. LOL

[MMonette]

I don't know if its too advanced for a "simple" machine but what about a pull-cart, then you have both a wheel and axel plus a fulcrum to move the loads. Perhaps something like this.

http://www.google.com/imgres?q=pull+...r:12,s:0,i:125

[letslearntogether47]

How about a fire piston?

[Wildthang]

Get a board and make a wooden A-Frame around 12" wide, 14" long and 16" - 18" high. Suspend a compound pulley on one side, and a simple single pulley on the other side. Get a cheap fish scale so you can attach it to either pully systems nylon string. Lift a 1 lb weight with the single pulley, and record the tension in lbs that it requires to lift the weight. Then do that using the compound pulley. The compound pulley will use much less tension to lift the same weight. It will look interesting, and show the advantage of simple machines at work. most or all of the material can be found at a home builders supply store.

[tjwilhelm]

The formal list of "simple machines" includes: Lever; Wheel and axle; Pulley; Inclined plane; Wedge; and, Screw.

The OP stated, "My boy (3rd grader) has to do a science fair project on simple machines..." Given that the word "machines" is plural, I wonder if it would be appropriate to do a project that incorporates several of the "simple machines" in a compound mechanism.

Also, keep in mind, the inclined plane, the wedge, and the screw, are all essentially using the same kind of mechanical advantage. Likewise, the wheel/axle and the pulley are very similar; and, the lever gives the same type of mechanical advantage as a Z-Rig or block-and-tackle set of pulleys.

I'd approach it this way: For a survival-related project, first choose a survival-related need that requires a mechanical advantage -- something that would require more brute strength than you have in your body to perform the task directly. Then show how to use one or more simple machines to fulfill that need/task. Some of the examples given above are good ones. I'm sure there are others, too.

Sample Scenario...a storm comes up and blows a dead tree trunk down onto your partner's leg. He's now injured and trapped, and the log is too heavy for you to just dead lift. A lever can be used to move the log off of your partner...OR...you can make a field expedient Z-Rig with a good, static safety rope and climbing-grade carabiners substituted for pulleys. I've done this when teaching tower rescue training. It works quite well.

FYI, a Z-Rig is similar in function to a block and tackle, except it's built with single pulleys (as opposed to a pulley block), or with just carabiners. The carabiners add friction; but, the mechanical advantage is still significant.

BRRR_Hauling_systems.jpg

[hunter63]

How about a simple travois?.....fore runner to the wheel.

[hikingpeter]

How about a fire piston?

This seems simple but is actually a thermodynamic machine. Essentially a reverse refrigerator, or the reverse of what happens when you discharge canned air or a CO2 cartridge. There's some sort of equation I can't remember how to use, like PV=nRT or something...