More Levers!

INTRODUCTION

Archimedes once said, "Give me a place to stand and I can move the world." What he meant was that if he could stand far enough away from the earth he could use a lever to move it. Levers use distance to make heavy objects easier to move. The goal of this experiment is to demonstrate how a lever reduces the amount of force needed to move objects.

MATERIALS

• 1 ruler
• 1 pencil
• 1 heavy book

VOCABULARY

Fulcrum: Point about which a lever turns or pivots
Effort arm: Distance from fulcrum to point where force is applied
Load arm: Distance from fulcrum to point where load is applied

WHAT TO DO

1. Use the pencil as the fulcrum and the wooden ruler as the lever. Place the pencil at the 6" mark on the ruler. Use a book as the load. Support a book at one end of the ruler. Push down on the opposite end of the ruler to lift the book.
2. Now place the pencil at the 9" mark on the ruler and repeat.
3. Now place the pencil at the 3" mark on the ruler and repeat.

QUESTIONS

1. Which position of the pencil makes it easiest to pick up the book?
2. How does the ratio of the effort arm/load arm affect the amount of force that must be applied?

SUMMARY

Levers lift objects easiest when the fulcrum is as close to the load end as possible.
Examples of other levers- Wheelbarrow, hammer, crowbar, seesaw, and the ring pull tops on a soda cans.

SOURCES

"Making Science Work: Forces and Machines." Terry Jennings, Raintree Steck-Vaughn Company, Austin, 1996. ISBN: 0-8172-3961-8.
"Investigate and Discover Forces and Machines." Robert Gardner, Julian Messner Press, Englewood Cliffs, 1991. ISBN: 0-671-69046-9.
"Starting with Science: Simple Machines." Deborah Hodge, Kids Can Press, Buffalo, 1998. ISBN: 1-55074-399-6.

© S. Olesik, WOW Project, Ohio State University, 2001.