Singha PrasitpongRatchapak ChitareeMahidol University2018-09-242018-09-242010-12-13AIP Conference Proceedings. Vol.1263, (2010), 66-69155176160094243X2-s2.0-78649900665https://repository.li.mahidol.ac.th/handle/20.500.14594/29938The frictional force is one of the obstacles to learning in physics. By itself, this topic consists of complicated ideas. In this study, we have investigated Thai students' ideas about directions and types of frictional forces by using open-ended questions and interviews. For example, these students believed that the direction of the frictional force always opposes to that of the motion or that of the external force exerted to such object. Moreover, most students thought that the frictional forces are resistant forces involving the object movement. They did not realize that sometimes the frictional force causes the object to move; has the same direction of the motion as well. About the kinetic friction, most students thought that if an object moves, it will always have the kinetic friction at the contact areas. From what we have found, we suggest that important steps for improving students' understanding of frictional forces is to teach students to draw free body diagrams, which can help students to visualize all forces acting on a single object. © 2010 American Institute of Physics.Mahidol UniversityPhysics and AstronomyConference PaperSCOPUS10.1063/1.3479895