Determination of skin friction on a rotating sphere in magnetic levitation
A simple and inexpensive experimental procedure is proposed to investigate the skin friction caused by air in a rotating sphere. A device using a magnetic field keeps the sphere levitating. The sphere is briefly boosted and begins to rotate, but the air resistance acts in opposition to the motion an...
| Main Authors: | , , |
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| Format: | Article |
| Language: | Portuguese |
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Sociedade Brasileira de Física
2024-02-01
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| Series: | Revista Brasileira de Ensino de Física |
| Subjects: | |
| Online Access: | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1806-11172024000100406&tlng=en |
| _version_ | 1797323544706678784 |
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| author | C. Cena L.F.S. Guizado J.V.B. Ferreira |
| author_facet | C. Cena L.F.S. Guizado J.V.B. Ferreira |
| author_sort | C. Cena |
| collection | DOAJ |
| description | A simple and inexpensive experimental procedure is proposed to investigate the skin friction caused by air in a rotating sphere. A device using a magnetic field keeps the sphere levitating. The sphere is briefly boosted and begins to rotate, but the air resistance acts in opposition to the motion and consequently the period of rotation increases. The experimental data demonstrate that the rotation period of the sphere increases exponentially with time. To account for this behavior, a physical model was developed, which provides an accurate description of the data. A coefficient, similar to the drag coefficient in the Drag Equation, was used to measure the air resistance on the rotating sphere. It is denominated as skin friction coefficient, its value was determined and it is remarkable that such a simple experiment provided a result so close to similar parameter value found in the literature. |
| first_indexed | 2024-03-08T05:30:09Z |
| format | Article |
| id | doaj.art-9c2f3c6d3a5f4ba895e5aa8af14201da |
| institution | Directory Open Access Journal |
| issn | 1806-9126 |
| language | Portuguese |
| last_indexed | 2024-03-08T05:30:09Z |
| publishDate | 2024-02-01 |
| publisher | Sociedade Brasileira de Física |
| record_format | Article |
| series | Revista Brasileira de Ensino de Física |
| spelling | doaj.art-9c2f3c6d3a5f4ba895e5aa8af14201da2024-02-06T07:40:44ZporSociedade Brasileira de FísicaRevista Brasileira de Ensino de Física1806-91262024-02-014610.1590/1806-9126-rbef-2023-0351Determination of skin friction on a rotating sphere in magnetic levitationC. Cenahttps://orcid.org/0000-0001-8766-6144L.F.S. Guizadohttps://orcid.org/0009-0008-7303-3459J.V.B. Ferreirahttps://orcid.org/0000-0001-9110-6457A simple and inexpensive experimental procedure is proposed to investigate the skin friction caused by air in a rotating sphere. A device using a magnetic field keeps the sphere levitating. The sphere is briefly boosted and begins to rotate, but the air resistance acts in opposition to the motion and consequently the period of rotation increases. The experimental data demonstrate that the rotation period of the sphere increases exponentially with time. To account for this behavior, a physical model was developed, which provides an accurate description of the data. A coefficient, similar to the drag coefficient in the Drag Equation, was used to measure the air resistance on the rotating sphere. It is denominated as skin friction coefficient, its value was determined and it is remarkable that such a simple experiment provided a result so close to similar parameter value found in the literature.http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1806-11172024000100406&tlng=enSkin friction coefficientdrag force coefficientsphere drag torque |
| spellingShingle | C. Cena L.F.S. Guizado J.V.B. Ferreira Determination of skin friction on a rotating sphere in magnetic levitation Revista Brasileira de Ensino de Física Skin friction coefficient drag force coefficient sphere drag torque |
| title | Determination of skin friction on a rotating sphere in magnetic levitation |
| title_full | Determination of skin friction on a rotating sphere in magnetic levitation |
| title_fullStr | Determination of skin friction on a rotating sphere in magnetic levitation |
| title_full_unstemmed | Determination of skin friction on a rotating sphere in magnetic levitation |
| title_short | Determination of skin friction on a rotating sphere in magnetic levitation |
| title_sort | determination of skin friction on a rotating sphere in magnetic levitation |
| topic | Skin friction coefficient drag force coefficient sphere drag torque |
| url | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1806-11172024000100406&tlng=en |
| work_keys_str_mv | AT ccena determinationofskinfrictiononarotatingsphereinmagneticlevitation AT lfsguizado determinationofskinfrictiononarotatingsphereinmagneticlevitation AT jvbferreira determinationofskinfrictiononarotatingsphereinmagneticlevitation |