The purpose of this study is to overcome the increased of critical thinking’ students after they used worksheet with STEM approach. This research method is experiment method that consist of preparing, implementation, and data processing. Increasing of critical thinking can be measured by pretest-posttest problems. The result of data normalization show that data have normal distributed so next test is n-gain test. Result of the n-gain test pretest-posttest scores around 0.5 (medium level categorized). The highest improvement is 0.9 at evaluation aspect and lowest increase is 0.3 at interpretation aspect.
Endapan pada minuman kopi tidak memiliki nilai daya guna yang tinggi. Telah dapat dilakukan upaya untuk memanfaatkan endapan minuman kopi sebagai pigmen organik untuk tinta spidol whiteboard. Pembuatan pigmen organik dilakukan dengan cara memperkecil ukuran partikel endapan minuman kopi menggunakan ball milling dan screen mesh. Proses pembuatan tinta dilakukan dengan mencampuran bahan-bahan pembuat tinta antara lain gum arab, aquades, alkohol, dan PEG pada pigmen organik. Proses pembuatan tinta dilakukan dengan variasi massa binder gum arab dari 1 gram sampai dengan 3,5 gram. Berdasarkan hasil pengujian, semakin banyak penambahan massa gum arab maka viskositas dan tingkat adhesi tinta akan bertambah. Sedangkan pada uji transmitansi, penambahan massa gum arab akan menurunkan nilai intensitas cahaya yang ditransmisikan oleh tinta.
We have successfully made a grating from a plastic bag, for use in diffraction experiments, by stretching the plastic bag with various weight forces providing a tensile force. The tensile forces result in empty spaces or slits in the plastic which are similar to the manufactured gratings for diffraction experiments. The experiment shows that the periodic diffraction patterns are formed and appear on the screen when coherent light of 532 nm passes through the grating formed in the plastic bag. The magnitude of the forces affects the distance between the slits of the grating in the plastic bag. According to this study, the larger the force, the larger the distance between the slits of the grating in the plastic bag. We measured the distance between the slits of the plastic bag grating produced by various masses as d 1 = (6.32 ± 0.09) × 10 −5 m for 500 g, d 2 = (6.99 ± 0.09) × 10 −5 m for 750 g, d 3 = (7.77 ± 0.20) × 10 −5 m for 1000 g, d 4 = (8.16 ± 0.13) × 10 −5 m for 1250 g, d 5 = (11.7 ± 0.11) × 10 −5 m for 1500 g. This work shows that a simple grating can be made from a plastic bag simply and used in proper experiments.
A teak leaf waste/polyurethane composite has been made for particleboard application. Some fraction variations are performed on the use of polyurethane as a matrix with a range of 0.04–0.20 (w/w). Mechanical and physical properties have been tested on the composites produced. The test results showed that the highest compressive strength of the sample reaches 38.5 MPa for polyurethane fraction of 0.14 (w/w). The composite has a density of 1261 kg m−3 which is in accordance with the result of density on teak. The physical properties have been also investigated and it was found that the lowest value of water absorption is 1.38%. This result indicated that the composites produced are potentially to replace wood raw material in eco-friendly industrial scale.
AbstrakKulit buah mahoni menjadi salah satu bahan yang belum termanfaatkan secara optimal dalam masyarakat. Jumlah kulit buah mahoni yang melimpah akan menimbulkan permasalahan baru berupa sampah. Tingginya jumlah kulit buah mahoni di lingkungan masyarakat menuntut cara penanganan alternatif yang kreatif dan inovatif menjadi produk berdaya guna. Sebuah upaya yang dilakukan adalah pemanfaatan kulit buah mahoni sebagai bahan komposit organik untuk kampas rem. Pembuatan bahan komposit dilakukan dengan mereduksi kulit buah mahoni hingga berbentuk serbuk karbon yang homogen yaitu dengan mengasap kulit buah mahoni menjadi arang kemudian dilakukan proses pencampuran sederhana dengan serbuk tempurung kelapa dan resin poliester sebagai bahan perekatnya. Kampas rem yang dihasilkan diuji kekerasan dan ketahanan aus dengan memvariasikan persentase komposisi serbuk arang kulit buah mahoni terhadap bahan penyusun lain. Terdapat lima variasi persentase komposisi bahan komposit yang dilakukan pengujian. Hasilnya diperoleh persentase komposisi paling tepat yaitu 60% arang kulit mahoni, 15% arang tempurung kelapa, dan 25% resin polyester yang memiliki nilai kekerasan dan massa keausan mendekati nilai Standar Nasional Indonesia (SNI).Kata-kata kunci: kulit buah mahoni, bahan komposit, kampas rem, uji kekerasan, uji gesek. AbstractMahogany bark is one of natural material which not used optimally in society. The overabundance of mahogany bark appearing new problem of garbage which charges an alternative solution creatively and innovatively becomes a new efficient and effective product. An alternative solution of mahogany bark utilization is as organic composite material of disk brake. The making of organic composite material of brake disk firstly is reducing the mahogany bark becomes a homogeneous carbon powder. The mahogany bark was smoked being of carbon and mixed with coconut shell and resin polyester as an adhesive. The organic composite material was produced, tested by Brinell Hardness test and attrition test by varied of composition percentage. There are five kinds of composite material composition had been tested. The result is obtainable of the most precise composition percentage 60% mahogany bark carbon, 15% coconut shell carbon, and 25% resin polyester which has brinell hardness number and attrition massa identically with Standar Nasional Indonesia (SNI).Keywords: mahogany bark, composite material, disk brake, Brinell hardness test, attrition test PENDAHULUANSampah menjadi salah satu permasalahan bagi kota-kota urban di Indonesia yang belum terselesaikan dengan baik hingga kini. Jumlah dan ragam sampah yang sangat banyak menjadi kendala bagi efektifnya pengelolaan sampah. Berbagai solusi telah diterapkan dalam penyelesaian permasalahan sampah seperti konsep daur ulang sampah berupa pembuatan kompos, biomassa, biodiesel, dan beragam pembenahan manejemen sampah. Dengan berbagai langkah inovasi
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