Measure the slope angle at which different rocks slide one over another (landslide)

Science Fair Project Information
Subject: Earth Sciences
Grade level: Elementary School - Grades 4-6
Academic Level: Ordinary
Project Type: Experimental
Cost: Low
Awards: First Place, Canada Wide Virtual Science Fair (2005)
Affiliation: Canada Wide Virtual Science Fair
Description: A hinged slope enables the change of the angle of the slope. A protractor attached to the base of the slope enables the measurement of the angle of the slope. Different rocks are mounted one onto another and the slope angle is changed until the slide begins in order to simulate a landslide.
Link: http://www.virtualsciencefair.org/2005/mcph5m0/public_html/index.html