Simple Machines

Levers

First Class

Give your students a ruler and a empty thread spool. Have them identify the fulcrum (spool) and then they can move it in different positions and see what effect it has on the amount of effort needed to perform the work. You can also go to the playground and experiment with a see-saw and have them move to different positions on the see-saw and note how that effects the effort. Other examples of things for them to explore are a hammer and crowbar.

Second class

Play with a wheel barrow. Have them identify where thee fulcrum, force and load is. How does a first and second class lever differ. Have them figure it out instead of telling them and they will remember better.

For the third class lever, you can have them help you with the chores -have them sweep the floor. Again, identify all the parts of the simple machine. They will laugh when they realize that the dirt is the load. You could also use a bottle opener or a shovel.

Wheels

Have them roll a small car across an uncarpeted floor. Note how far it went. Now flip it over and give the same push. Note the difference. You can go outside and do the same with a wagon. They can make a simple wheel and axle from a plastic lid of a coffee can and a pencil. Poke a pencil through the center of the lid. Hold both sides of the pencil and rote the lid across the floor. Go for a walk and seek out wheels. This brings out an awareness of just how much we use them.

Pulleys

Always teach them to figure out the parts of each simple machine. It makes them think about how they work. Pulleys can be bought at a hardware store. Have them notice how much easier it gets as they add additional pulleys but how much more rope they need. You can measure this precisely or just judge it by the eye. (Additional pulley demonstration can be found here.)

Inclined Planes, Screws and Wedges

They quickly figure out this is the same as a ramp. They enjoy exploring mechanical advantage by using a toy truck and a rubber band. Tie it to toy truck and hold it straight up in the air by the rubber band. Hold a ruler up beside it and measure the number of inches it stretches. Next, make a ramp with a board held up by something and pull the truck up it with the rubber band. Hold the ruler up to it, and notice how far it stretches. Change how steep the ramp is and repeat the experiment. Change the length of the board. My boys could experiment in this way for a long time.

Build a model of a mountain out of clay. Have them pull a very small toy car up it with a rubber band attached. Now make a path in the mountain that goes upward, circling around it in a spiral. Now have them pull the car up. Is it easier the second time around? It is easy to see how a screw is an inclined plane by looking straight down at this.

Have them experiment with different size screws and screwdrivers. Do they discover a connection between size and effort?

It is natural for them to see that a wedge is the same thing as an inclined plane -just a difference in how it is used. Have them discover that some wedges join things together (nail, for example)and some split materials apart (axe or scissors), and some hold things in place (door stop.) Provide them with triangle blocks to experiment with. How else can they be used besides the ramp?

Have them look at a complex machine, such as a bike, and identify the simple machines within it.

Have them narrate with drawings as they learn.

We were studying Ancient Egypt and Stone Henge at the time, so we thought a lot about and researched how they built them using simple machines.

I love this simple activity at Imagine Childhood in which  they used bricks sticks, stones and sting and played around with stone fulcrums and levers, wooden wedge sticks and counterweights, to raise the bricks off the ground little by little and lever arms to see how much easier it would be to move and turn the stone on the ground.  First they tried using just the stone, and then they added lever arms and some sand underneath to reduce friction. See how many terms can be taught with this simple activity?

Once you get them started, they will find their own explorations and make all sorts of connections.

I love this idea at Irresistable Ideas for Play Based Learning of setting up pulleys in a play area to let children make their own discoveries about them.
They also show using rollers.