##### Objectives
• Students will use observation skills to draw conclusions.
• Students will learn the usefulness of levers and the scientific reasoning behind them.

##### Materials
• Short pencil
• Tape
• Plastic bag
• Small stones
• Shoe box
• Two equal lengths of wood, or two rulers
##### Procedure

Force X Distance = Work (Write this on the board.)

Look at the equation. If force and distance are small, like when you're turning the pages in a book, then work is small. What would happen if the distance were zero? No work would be done, no matter how much force was applied. Pushing against a wall may use a lot of force, but unless the wall actually moves, no work is being done.

There are a lot of simple machines, like levers, pulleys, and ramps, that make it so that you don't need to use as much force to do the same amount of work. How do they do this? Well, they increase the distance over which the work is done. Have you ever sat on a see-saw with an adult much heavier than you? You know that there is no way you could have lifted the adult using just your arms. But by sitting on the very end of the see-saw, you were able to lift a person much heavier than yourself. The see-saw is a lever that helps you do the work by spreading the force you apply over a greater distance.

Instructions for the Project:

2. Put the stones in the plastic bag and lift them.

3. Observe the amount of force, or effort, you must exert to lift the stones.

4. Tape the two pieces of wood or two rulers to the bottom of the box, one on either side. Leave the ends sticking out, like wheelbarrow handles.

5. Make a wheel by sticking the pencil through the spool.

6. Tape the pencil crosswise to the ends of the wood.

7. Put the bag of stones in the barrow, close the the wheel. Try lifting it. It's easier to lift the stones when they are in the wheelbarrow than it was to lift them without the wheelbarrow. The wheelbarrow acts as a lever. When you use a lever, your hands move farther than the distance the load moves. The amount of force you need to use to lift the stones is less, but it is spread out over the longer distance created by the lever.

Brought to you by Tom Snyder Productions

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