The purpose of this study was to determine effects of Problem Based Learning (PBL) on the academic achievements stability in Physics of Yefren -Libya primary school (seven class) by a physics test designed by the researcher, This study used the descriptive analytical method after data collection by questionnaire and evaluation test on the occasion of this type of approach to such research studies, Results showed a statistically significant difference between the mean scores of the two sets of

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... udy in the stability of the achievement test dimensional, and that was the difference for the experimental group which studied students of physics in a way of problem based learning (PBL)