1. Title:Energy Thief

2. Purpose:To determine how much energy is lost to friction on the marble coaster.

3. Materials:Foam track, marble, meter stick, masking tape, supports for track, spreadsheet

4. Procedure:

a. Set the track up as shown in the illustration. Raise both ends of the track to a height of about 1 meter above the floor or lab table. Tape the track to the floor or table and the supports to prevent it from breaking.

b. Mark a starting point with a piece of tape. Consider this point A. Record the height (h1) in centimeters.

c. Release the marble from point A. and mark with a piece of tape the height that it reaches on the uphill slope. Consider this point B. Record the height (h2) of point B on the data table.

Repeat 3 times for each position until the first 2 columns are complete.

5.Data Table

Position#	Starting Height (h1)	Final Height (h2)	Efficiency (h2/h1)x100%	% Lost to friction
1
1
1
2
2
2
3
3
3
4
4
4
5
5
5
			Ave Eff=	Ave%lost =

6. Data analysis: (Describe your data and results.)

a.Use the spreadsheet to calculate the % of efficiency and the % of energy lost to friction.

At the bottom of each column, calculate the average of each.

b. What patterns do you see?

7. Conclusion: (Why did you get these results?)

8. Other Questions

a. Why was it necessary to keep the track from moving sideways?

b. Examine the data table. Is h2 ever greater than h1? Explain why or why not?

c. If the marble-track system were frictionless, how far up the track would the marble travel?

d. If the track is 80% efficient, where does the other 20% of the energy go?

e. What factors would influence the amount of friction experienced by the marble-track system?

9. Opinion: (I liked or did not like this lab because .....)

The more friction between the marble and the track, the less efficient the marble-track system. The more energy the marble uses to overcome friction, the less it has to make it up the hill.

The amount of energy retained by the marble during its trip can be found by determining the ratio of h2 to h1. This ratio of h2 to h1 is the "efficiency" of the marble-track system. For example, a frictionless system would be 100% efficient and a 70 % efficient system would lose 30% of its potential energy to frictional forces.

Potential energy is determined by mulitplying mass x gravity x starting height. In this experiment, mass and gravity are constant. Thus, only the heights need to be compared.

efficiency = (h2/h1) x 100% = Potential Energy at Point B/Potential Energy at Point A

To compare h1 (starting height) to h2 (final height) is to compare the starting potential energy with its final potential energy at h2. The loss due to friction = 100% - efficiency.

CREDIT: Adapted from materials presented at a Florida Association of Science Teachers conference (1995) by T. Griffith Jones from P.K. Yonge Developmental Research School, University of Florida

Also see: Crazy Coasters published by Science Kit & Boreal Laboratories, 777 East Park Drive, Tonawanda, NY 14150-6784