Use a simple machine called a lever! To build your own lever and see one in action, try this Science Lab.
You can also check out another Science Lab.
|What You Do|
|1. Learn about levers.|
|2. Read my Science Lab on levers and think about the challenge question.|
|3. Predict with your classmates how you think this balancing act might be accomplished.|
|4. Do the experiment.|
|5. Share your results with the rest of your class.|
Science Lab on Levers
What do a fork, a pair of scissors, and the little handle that flushes your toilet have in common? Well, apart from being common devices found in most modern households, they're all levers, and levers are some of the most important machines going. They've been around for thousands of years.
Simply put, levers are machines used to increase force. We call them "simple machines" because they have only two parts ó the handle and the fulcrum. The handle or bar of the lever is called the "arm" ó it's the part that you push or pull on. The "fulcrum" is the point on which the lever turns or balances. In the case of a fork, the fulcrum is the fingers of your hand. Scissors are really two levers put together. The handle on the toilet flusher is commonly called a fixed lever. Take a quick look around you and see how many levers you can find.
To build your own lever and see one in action, try my Science Lab.
Here's what you'll need:
ï a 30 cm (12 inch) plastic or wooden ruler
ï 10 pennies (All pennies should be newer than 1990. Can you figure out why?)
ï a pencil
ï a level desk or table top
|Here's what to do:|
|1. Lay down the pencil flat on the desk.|
|2. Lay the ruler across the pencil so that the two ends of the ruler teeter back and forth like a see saw.|
|3. Adjust the ruler on the pencil so that the two ends balance perfectly. The balance point should be at about the 15 cm (6 inch) mark.|
|4. Stack 5 pennies at the very edge of the ruler on the 1 cm (1 in.) side and the other 5 pennies on the very edge of the 30 cm (12 inch) side. Since the two piles of pennies are about equal in weight, the two ends of the ruler should remain balanced.|
|5. Take three pennies off of the 30 cm (12 inch) side and place them on the stack at the 1 cm (1 inch) side. You should now have 8 pennies on one side and 2 on the other. The ruler should be tilted down toward the 1 cm (1 inch) side. You've just constructed a lever!|
How can you lift four times your weight? Try it with these pennies! Without adding any weight to either side and without moving the pennies, can you figure out how to get the two ends of the ruler to balance? (Note: The ruler doesn't have to balance exactly ó it just needs to be at the point where it teeters back and forth without touching the desk.)
Before you try this Science Lab, predict what will happen with your classmates. When you've finished the Science Lab, share your results with the rest of the class.