Galileo's Inclined Plane Experiment:

Repeated by the Rice Galileo Experiment Team.

I. Construction of the Materials

Ball
The ball was a 5/8" steel ball bearing.

Inclined Plane
At a 45 degree angle, the edges of two 16 foot 2X4's were planed off, such that, when placed together,they formed a groove a little greater than a finger width's wide. The planed edge was meticulously sanded to be perfectly smooth with five increasingly fine pieces of sandpaper. The sanded edges were then rubbed with linseed oil and left to dry for 24 hours. Linseed oil was reapplied three times, with 24 hour drying periods between them. The boards were then nailed together such that there was a groove between them. At the end of the plane, a piece of brass was nailed to stop the ball, and make a loud noise when the ball reached the end of the plane.
A camera tripod was used to hold the plane at a 5 degree angle.

Water Clock
A small hole was drilled in a 2 gallon plastic bucket through which was threaded a piece of plastic tubing, 1/4" in diameter. The hole was checked for leaking, and proved to be water tight. A clamp was placed on the tubing such that when in place, no water could go through the line. A line was drawn at the nearly full mark, and the water level was kept at this mark throughout the experiment.
A 200 ml beaker was used to catch the water coming from the bucket. The beaker was weighed on an electric balance accurate to one decimal place.

II. Experimental Procedure

  1. The beaker was weighed five times during the experiment on an electronic balance.
  2. Distance markers were drawn, with a thin pencil, at 1/4, 1/2, 3/4 and the full length of the inclined plane.
  3. The ball was positioned such that it's center was aligned with the full length distance marker. The ball was held by gently supporting it with two index fingers perpendicular to the groove of the board.
  4. The person operating the water clock said "GO" and the ball holder simultaneously released the ball.
  5. When the water clock operator said "GO," she simultaneously squeezed the clamp to allow water to flow freely into the beaker.
  6. When the water clock operator saw and heard the ball hit the metal piece at the end of the board, she released the clamp, stopping the water flow to the beaker.
  7. The water clock operator then placed the beaker on an electronic balance, and the recorder recorded the weight of the beaker plus water.
  8. The water was returned to the bucket, and the beaker meticulously dried.
  9. This procedure was repeated 20 times.
  10. Then the ball was released from 3/4 the length of the plane, and repeated 20 times, and so on.

III. Data:

Weight of beaker: 50.4g

Trial Full length 3/4 1/2 1/4
1 33.3* 31.3 21.9 18.1
2 35.1 30.6 21.9 19.0
3 32.9 29.7 27.0 19.7
4 34.0 30.7 25.9 19.4
5 33.7 30.4 27.3 16.3
6 34.1 27.4 26.8 17.7
7 34.5 28.3 27.1 20.0
8 33.6 30.2 25.8 18.7
9 34.8 31.4 28.3 18.4
10 33.7 23.6 27.3 15.6
11 35.3 26.5 27.3 13.9
12 34.6 28.8 27.4 13.7
13 35.2 28.7 26.6 17.4
14 32.8 28.7 22.6 16.4
15 35.4 29.6 25.0 16.2
16 33.5 23.8 24.9 14.3
17 35.1 24.5 22.5 15.6
18 33.2 27.9 25.5 17.3
19 35.5 30.5 20.8 17.3
20 34.3 27.9 25.2 16.9
Mean 34.2 25.5 25.4 17.1
Standard Deviation
of the Mean 		0.87 2.37 2.23 1.86
*Numbers given are grams of water collected in the beaker.

Return to overview of inclined plane.

Last revised April 17, 1995

Jennifer Lacy

jbl@owlnet.rice.edu