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Project Summary

Difficulty	2
Time required	Very Short (a day or less)
Prerequisites	Basic understanding of gravity
Material Availability	Readily available
Cost	Very Low (under $20)
Safety	Adult supervision required when using ladder

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Abstract

Objective

The goal of this project is to repeat Galileo's famous experiment to answer the question: do heavier objects fall faster than lighter ones?

Introduction

In 1589, a young scientist and mathematician named Galileo Galilei conducted a simple experiment. Galileo dropped two iron balls of different masses from great height to see which ball hit the ground first. This experiment challenged a 2000 year-old idea proposed by the philosopher Aristotle who believed that heavier objects fall faster than lighter objects. Aristotle thought that a ball that was 10 times as heavy as another ball would fall 10 times as fast. Neither Aristotle nor any one else had ever tested to see if his idea was correct.

Galileo proved Aristotle wrong when he dropped a 10 pound ball and a 1 pound ball from the top of the Leaning Tower of Pisa, and a crowd watched them hit the ground at the same time. Galileo's experiment showed that experimentation is necessary to test scientific theories.

Terms, Concepts and Questions to Start Background Research

• Galileo
• motion
• gravity
• mass
• acceleration

Questions

• What force causes all objects to fall to the ground?
• Where does this force come from?

Bibliography

• A Collection of Famous Experiments Written for Kids:
  Filson, Brent. 1986. "Famous Experiments and How to Repeat Them," Julian Messner, NY.
• Introduction to General Physics Concepts:
  Hewitt, Paul G. 2002. "Conceptual Physics," Prentice Hall, IL.
• Simple Physics Concepts for Kids: Keller, R.W. 2005. "Real Science for Kids: Physics, Level 1," Gravitas Publications, Inc., NM.

Materials and Equipment

• two balls of the same size, but different mass
• a ladder or step stool
• a video camera (optional)

Experimental Procedure

1. Set up the video camera to record the experiment (optional). Make sure to state for the camera each trial number.
2. Climb the ladder and prepare to drop both balls from the same height at the same time.
3. Drop the balls and record the results in a data table by checking off which ball hit first.
4. Did one ball hit the ground before the other? Did they hit at the same time? View the video recording to verify your results.
5. For any experiment, it is important to do multiple trials to assure that your results are consistent. Repeat the experiment at least ten times, and record your results. It will be easier to keep track of your results if you write them down in a table in your lab notebook. Here is an example table for data collection:
   

   Sample Data Table
   Trial #	Heavy Ball	Light Ball	Same Time
   1
   2
   3
   4
   5
   6
   7
   8
   9
   10

Variations

• Try balls of the same mass, but different sizes.
• Try objects of the same mass but different shape.
• Try objects of different shape, size, and mass.

• For more science project ideas in this area of science, see Physics Project Ideas.

Credits

La Né Powers

Last edit date: 2006-02-22 00:44:48

Career Focus

If you like this project, you might enjoy exploring careers in Physics.

Physicist Physicists have a big goal in mind—to understand the nature of the entire universe and everything in it! To reach that goal, they observe and measure natural events seen on Earth and in the universe, and then develop theories, using mathematics, to explain why those phenomena occur. Physicists take on the challenge of explaining events that happen on the grandest scale imaginable to those that happen at the level of the smallest atomic particles. Their theories are then applied to human-scale projects to bring people new technologies, like computers, lasers, and fusion energy.

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