## 5 Conclusions  
In this paper we analyzed the perceptions and attitudes that online students have regarding videos in an online physics course, specifically, videos where the teacher's hands appeared in writing on a blackboard and videos where the hands did not appear. The method followed has been an analysis of interviews from a ground theory perspective. Thus, semi-structured interviews have been performed until saturation to validate hypotheses but also to look for new knowledge that would help explain the relation between students and videos in the classroom.  
We found that videos are perceived as an extra resource available in physics and students use them combined with the rest of the available resources. Videos are the resource that they prefer because they facilitate and accelerate understanding of the concepts of physics and offer high interactivity. An indicator that they consider videos useful is that they watched them several times.  
However, students considered the most important resource to be text documents because of their completeness, rigor and easiness to review. Therefore, we think that a physics course cannot be structured only around videos.  
Online students find that human elements are also very important in an online environment. In fact, they find that hands in the video play this human role. But hands in the video also play the role of being an important element to attract attention, pointing to where the students should look, for example. Therefore, videos with hands are able to introduce a human element with an active role within the video.  
Regarding the physics course, it includes theory and problems and, therefore, students have available videos of theory and videos of problems. We have found that students consume both of them and find that both are important. On the other hand, the consumption of videos is related to deliveries and exams and students watched the videos more frequently when they had these milestones.  
Thus, from this study we conclude that videos play a key role in online physics courses, although they are considered a complement to other materials. Therefore, they should be augmented with other resources such as text documents according to students' preferences. Videos with hands are more adequate than videos with the teacher's face since they may address two necessary needs: provision of human element to create a social link among students and teacher and a pointing (mimic) element that focuses the attention of students or allows them to relate to relevant elements.  
As future work, we plan to contrast these perceptions with the data collected from the use of the videos.  
Conceptualization, A.P.-N.; videos, A.P.-N.; methodology, A.P.-N., V.G. and J.C.; interviews: A.P.-N., V.G. and J.C.; formal analysis, A.P.-N.; investigation, A.P.-N., V.G. and J.C.; data curation, A.P.-N., V.G. and J.C.; writing--original draft preparation, A.P.-N. and V.G.; writing--review and editing, A.P.-N., V.G. and J.C. All authors have read and agreed to the published version of the manuscript.  
This research was partially funded by the European Commission through the project \"colMOOC: Integrating Conversational Agents and Learning Analytics in MOOCs\" (588438-EPP-1-2017-1-EL-EPPKA2-KA).  
Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.  
The data presented in this study may be available on request from the corresponding author, although it can be slightly modified and cut due to privacy reasons.  
One of the authors, [PERSON], wants to thank eLearn Center at UOC and to [PERSON] for the support in the creation of the videos. All the authors want to thank the students that participated in the interviews.  
The authors declare no conflict of interest.
Figure 17: Structure of the interview (II).  
Figure A4: Structure of the interview (IV).