Fragmentation Experiment and Model for Falling Mercury Drops

The experiment consists of counting and measuring the size of the many fragments observed after the fall of a mercury drop on the floor. The size distribution follows a power-law for large enough fragments. We address the question of a possible crossover to a second, different power-law for small enough fragments. Two series of experiments were performed. The first uses a traditional film photographic camera, and the picture is later treated on a computer in order to count the fragments and classify them according to their sizes. The second uses a modern digital camera. The first approach has the advantage of a better resolution for small fragment sizes. The second, although with a poorer size resolution, is more reliable concerning the counting of all fragments up to its resolution limit. Both together clearly indicate the real existence of the quoted crossover. The model treats the system microscopically during the tiny time interval when the initial drop collides with the floor. The drop is modelled by a connected cluster of Ising spins pointing up (mercury) surrounded by Ising spins pointing down (air). The Ising coupling which tends to keep the spins segregated represents the surface tension. Initially the cluster carries an extra energy equally shared among all its spins, corresponding to the coherent kinetic energy due to the fall. Each spin which touches the floor loses its extra energy transformed into a thermal, incoherent energy represented by a temperature used then to follow the dynamics through Monte Carlo simulations. Whenever a small piece becomes disconnected from the big cluster, it is considered a fragment, and counted. The results also indicate the existence of the quoted crossover in the fragment-size distribution.Comment: 6 pages, 3 figure

O livro didático de sociologia no ensino médio: Uma análise na perspectiva da “colonialidade do saber”

TCC (graduação) - Universidade Federal de Santa Catarina, Centro de Filosofia e Ciências Humanas, Curso de Ciências Sociais.A partir do momento em que se tornou obrigatória no ensino médio brasileiro, muito tem sido discutido e pensado sobre a disciplina de Sociologia que vai à escola. Ao pensarmos seu ensino de forma criteriosa surgem, também, questões que vão além de seu debate metodológico, envolvendo os dilemas epistemológicos dessa disciplina. Podemos dizer que os saberes sociológicos escolares são, basicamente, os saberes sociológicos acadêmicos transpostos. Nos saberes acadêmicos por sua vez, percebe-se a tendência à valorização do conhecimento com um lócus de enunciação determinado e que considera como verdadeiro e válido uma forma específica de saber. Ao desconsiderar todas as outras formas de conhecimento, tal mecanismo reproduz uma visão única da história, perpetuada pela “colonialidade do saber”. Dessa forma, o presente artigo tem por objetivo caracterizar tais “colonialidades” do/no ensino de Sociologia, através, sobretudo, da análise de um dos livros escolhidos pelo Plano Nacional para o Livro Didático: “Sociologia para o Ensino Médio” de Nelson Dacio Tomazi (2010).From the moment it became mandatory in the Brazilian school system, much has been discussed and thought about the Sociology disciplines that arrive at high schools. When we carefully think about the teaching of this subject, questions rise beyond the methodological debate, leading to epistemological dilemmas involved. High school sociological knowledge is basically a transposed academic sociological knowledge. It is noticeable that the academic view tends to appreciate the knowledge from a determined enunciation locus, and also that only one specific form of knowledge is considered true and valid. When it disregards all other forms of knowledge, such mechanism reproduces only one version of history, perpetuated by the “coloniality of knowledge”. Thus, the present article has the purpose of characterizing such “colonialities” in and of the Sociology’s teaching, through and above all, the analyzes of the book chosen by the “Plano Nacional do Livro Didático” [the brazilian National Plan for the Didactic Book]: “Sociologia para o Ensino Médio” [Sociology for High School], from Nelson Dacio Tomazi (2010)