## 1 Introduction  
Nowadays, the use of videos is the most common type of social medium [1] and is used in class and published online [2].  
However, creating videos is a very challenging task that requires many hours and resources for just a few minutes of video [3]. Teachers usually lack the skills to create videos with a professional look and the literature shows that teachers find it easier to create videos by recording their classrooms since this is the closest scenario to their abilities. Nevertheless, this kind of video is not the most useful for students since they have the lowest engagement [4] and they are often too long which lowers student engagement [5]. Thus, it is important to find out which videos are useful for students but are also easy to create for teachers.  
Our main hypothesis is that creating videos filming the hands of the teacher while they are writing on a paper (or on a blackboard) satisfies those requirements, since they look similar to how teachers explain when a student attends to discuss items with them privately. We call these videos, videos with hands. We think that videos with hands also satisfy another important aspect which is the emotional link with the teacher [6], and the provision of non-verbal communication [7].  
On the other hand, students of science and engineering at Universitat Oberta de Catalunya (UOC), and potentially at any online university, have greater difficulties in completing their academic program in comparison to students from other disciplines (i.e., the dropout rate is higher in those disciplines [8]). Within science and engineering, a physics course offers a stressful scenario to students because it is a challenging course for most [9], with a high load in mathematics, which is accentuated in the case of 100% online universities because of the difficulties of distance education [10].  
In this work, we analyze students' perception regarding videos in an introductory course in physics in several studies of engineering at a university that is 100% virtual (UOC). This analysis will allow us to understand if students perceive videos as a useful resource. Physics is a challenging scenario in which the role of videos could be more critical. In addition, analysis of the physics course allows comparing different kinds of pedagogical videos: (1) theory videos, in which a concept is introduced; and (2) videos of problems, which present a challenge, a problem or an exercise and explain how to solve it using the tools explained in the theory videos.  
To perform the analysis, a qualitative approach was taken, from the grounded theory perspective [11]. Students' perception was obtained thorough the analysis of semi-structured interviews, according to the Wengraf spectrum (referenced by [12]), following an approximation hypothetic-inductive.  
This is exploratory research to understand the interaction between students and the video in introductory physics courses from the students' point of view. As far as we know, this is the first time that interviews were used as the method to learn about attitudes and perceptions of students regarding videos in a physics online course. According to [PERSON], [PERSON] and [PERSON] (1975), this qualitative approximation involves an empathic understanding and has the ability to represent thoughts, feelings and motivations of the students [12].  
The paper is organized as follows. This section presents a literature review regarding the use of video as a pedagogical tool, the importance of using human elements like hands in videos, the suitability of these videos in the specific features of physics courses and the hypotheses of the research. In Section 2 the methods are shown. In Section 3 the results obtained are shown and Section 4 presents the conceptual/causal matrix and mapping tree, discusses the gathered knowledge and analyzes if results are compatible with the hypotheses. The paper concludes with Section 5.