Prior knowledge that students have can be compatible with scientific facts or it can be a learning disability different from the scientific facts. So it is important to reveal students' prior knowledge and to determine their ideas that are not compatible with scientific information. In this study, it has been aimed to reveal the prior knowledge of 133 tenth grade students about torque, conservation of angular momentum and Kepler's 2nd law. Students taking place in the sample have not taken formal education about these concepts yet and their ideas may be naive. The students have been asked three open-ended questions whose study of validity and reliability has been carried out. While it is seen that students gave answers consistent with the scientific facts about the torque concept, none of the answers given by students about the conservation of angular momentum and Kepler's 2nd law is included in the category of scientific answer. Students have been encountered the most common type of alternative answers for both of these concepts. In the teaching of this concept and law, students' prior knowledge conflicting with the scientific ideas should be considered, that is to say, teaching should be organized to include conceptual change.