Mulailah

Tanpa permulaan, anda tidak akan sampai ke mana-mana.

Semangat

Semangat yang kuat mampu mengatasi apapun cobaan yang datang.

Konsisten

Lumbung emas dalam diri kamu adalah pikiran kamu. Kamu dapat menggalinya sedalam-dalamnya dan sepuas-puas yang kamu inginkan.

Pantang Menyerah

Gagal selepas usaha adalah hikmah, anda akan mendapat sesuatu yang lebih besar daripada apa yang anda sangkakan.

Be The One

Be the one is better than be the best.

Friday, January 6, 2012

Pengertian Energi, Potensial, Kinetik dan Hukum Kekekalan Energi - Fisika

Energi dari suatu benda adalah ukuran dari kesanggupan benda tersebut untuk melakukan suatu usaha. Satuan energi adalah joule. Dalam ilmu fisika energi terbagi dalam berbagai macam/jenis, antara lain :
- energi potensial
- energi kinetik/kinetis
- energi panas
- energi air
- energi batu bara
- energi minyak bumi
- energi listrik
- energi matahari
- energi angin
- energi kimia
- energi nuklir

- energi gas bumi
- energi ombak dan gelombang
- energi minyak bumi
- energi mekanik/mekanis
- energi cahaya
- energi listrik
- dan lain sebagainya

A. Energi potensial atau Energi Diam
Energi potensial adalah energi yang dimiliki suatu benda akibat adanya pengaruh tempat atau kedudukan dari benda tersebut. Energi potensial disebut juga dengan energi diam karena benda yang dalam keaadaan diam dapat memiliki energi. Jika benda tersebut bergerak, maka benda itu mengalami perubahan energi potensial menjadi energi gerak. Contoh misalnya seperti buah kelapa yang siap jatuh dari pohonnya, cicak di plafon rumah, dan lain sebagainya.
Rumus atau persamaan energi potential :
Ep = m.g.h
keterangan
Ep = energi potensial
m = massa dari benda
g = percepatan gravitasi
h = tinggi benda dari tanah
B. Energi Kinetik atau Kinetis
Energi kinetik adalah energi dari suatu benda yang dimiliki karena pengaruh gerakannya. Benda yang bergerak memiliki energi kinetik.
Rumus atau persamaan energi kinetik :
Ek = 1/2.m.v^2
keterangan
Ep = energi kinetik
m = massa dari benda
v = kecepatan dari benda
v^2 = v pangkat 2

C. Hukum Kekekalan Energi
" Energi tidak dapat diciptakan dan juga tidak dapat dimusnahkan "
Jadi perubahan bentuk suatu energi dari bentuk yang satu ke bentuk yang lain tidak merubah jumlah atau besar energi secara keseluruhan.
Rumus atau persamaan mekanik (berhubungan dengan hukum kekekalan energi) :
Em = Ep + Ek
keterangan
Em = energi mekanik
Ep = energi kinetik
Ek = energi kinetik
Catatan :
Satuan enerti adalah joule

Bilangan Hampir Bulat

Banyak bentuk operasi pada bilangan di dalam matematika yang nilainya hampir bulat. Contohnya, sin 11 = −0,999990206… (hampir sama dengan −1). Bilangan-bilangan hampir bulat dengan operasi-operasi tidak sederhana (bukan operasi Aritmetika biasa: tambah, kurang, kali, & bagi), seperti fungsi trigonometri, penarikan akar, logaritma, kaitan dengan bilangan-bilangan irrasional (e, p, dll) dalam matematika kadang disebut sebagai Bilangan Hampir Bulat (almost integer). Satu yang menarik, bila kita melakukan perhitungan dengan bilangan-bilangan tsb kita bisa tertipu pada hasil perhitungannya, sekalipun menggunakan kalkulator (yang umumnya terbatasi pada ketelitian tidak lebih dari 10 atau 12 angka). Contoh lainnya:
cos (ln (p+20)) = - 0,9999999992…(hampir - 1)
22p4 = 2143,000002748… (hampir 2143)
510 10log 7 = 431,00000040… (hampir 431)
3Ö2(Ö5 2) = 1,0015516… (hampir 1)
Sekarang cobalah menemukan panjang d pada
bangun di bawah ini.



Jika Anda mencoba mengukurnya, maka Anda akan menjumpai bahwa d = 7. Tidak peduli, apakah Anda mengukur dalam ukuran meter lalu teliti hingga ke ukuran micrometer sekalipun. Karena, ukuran sesungguhnya d = 7,00000008574…


artikel sandur dari buletin RINGAN edisi maret 2007

Mobile Perspectives: On teaching Mobile Literacy

David Parry
David Parry (dparry@utdallas.edu) is Assistant Professor of Emerging Media and Communications at the University of Texas at Dallas.

Comments on this article can be posted to the web via the link at the bottom of this page.
"The future our students will inherit is one that will be mediated and stitched together by the mobile web, and I think that ethically, we are called on as teachers to teach them how to use these technologies effectively."
In the book Smart Mobs, Howard Rheingold argues: "The mobile internet . . . will not be just a way to do old things while moving. It will be a way to do things that couldn't be done before." In part because of this, he then suggests: "A new kind of digital divide ten years from now will separate those who know how to use new media to band together from those who don't."1 Rheingold wrote that in 2002. In other words, that ten-year horizon has nearly expired. While recognizing that digital access is not evenly distributed in the United States, which is to say nothing of the global distribution, we can safely say that this transformation is already here; we are already at the moment in which the ability to use social media, and particularly social media as amplified through the power of the mobile web, has become a key literacy. (Literacy here is perhaps the wrong term, for the skills needed to navigate and take ownership of these spaces far exceed the comparatively simple skill of comprehending written text.)
What makes this moment ever more complicated is that just as we have introduced computers into the classroom—just as we have started to come to terms with the idea of wired learning spaces, mediated laptops, and occasionally the now-dinosaur-like desktops—the mobile web is about to make all this technological adaptation rather outdated. The unwired learning space is about to substantially alter the landscape of teaching with and through technology. As my colleague Dean Terry likes to point out, we are in the "Late Desktop Era."2 Some educators have responded by banning this new technology from the learning space, demanding that students turn off their smartphones and keep their tablet computers stowed in their bags. This approach, I would suggest, is precisely the wrong tack to take. The future our students will inherit is one that will be mediated and stitched together by the mobile web, and I think that ethically, we are called on as teachers to teach them how to use these technologies effectively, to ensure that they end up on the right side of the digital divide: the side that knows how to use social media to band together. Teaching mobile web literacy seems to me as crucial as teaching basic literacy.
To be sure, I am not suggesting that educators encourage students to text each other during class. Instead, I feel that one of our obligations as educators is to consider how the mobile Internet changes not only how we teach, but what it means to be knowledgeable and educated in our culture. And just as important, the mobile web opens up a host of pedagogical possibilities. Let me sketch out a few literacies that we ought to be striving to teach our students:
"Teaching mobile web literacy seems to me as crucial as teaching basic literacy."
1. Understanding Information Access. A mobile web often creates a situation in which information is quickly and easily available online. Within the classroom, this means nearly any bit of factual information we need is accessible in a matter of seconds—if one knows how to navigate the web efficiently. Frequently I will say in class: "I am not sure: look it up." I do this for several reasons. First, I often do not know things, and I think admitting to not knowing is good modeling for students. But second, in articulating this not knowing, I am inviting students to practice the skill of information access and see this activity as a valuable part of academic conversation (and not just as the fastest way to answer any trivia question). This task can be effective even in a wired classroom, using desktop computers or laptops, but having students use mobile devices demonstrates to them how finding information is not contingent on access to a not-so-mobile device. They are therefore able to practice the skill of quick information access and credibility detection—a skill that will be useful throughout their lives regardless of what they choose to do professionally.
2. Understanding Hyperconnectivity. I often encourage students to Twitter during class. This is not to suggest that I ask them to ignore what is occurring in the classroom space in favor of following a Twitter stream; rather, as a class exercise, students often tweet about what is going on during class. This serves as both a collaborative note-taking exercise3 and a demonstration of how conversation can be extended beyond the classroom space, similar to the way Twitter is now a popular tool at conferences. But there are also times in class when we will talk about how engaging in this type of hypermediated experience can distract from directing full attention to a particular event. Again, one of my goals is to teach students when and how to effectively use this technology.
3. Understanding the New Sense of Space. This is perhaps the most important and also perhaps the hardest literacy to explain. I am not sure that our society has become fully aware of the degree to which geo-location and the mobile web will change our daily practices. Web services like Gowalla (http://gowalla.com/) and FourSquare (http://foursquare.com/) are just the very beginning of the massive amounts of data that we are going to be layering on top of the physical world and that will substantially alter how we can interact with space. Even augmented reality applications such as Layar (http://www.layar.com/) and Wikitude (http://www.wikitude.org/en) are just the initial offerings in what is going to become an increasingly complex, data-rich landscape. So here, again, my goal is to get students to begin to understand how one can use a mobile device to both create and access spatial information. When our class reaches the point during the semester at which we discuss the increasing prevalence of cameras in our daily life, I have students use their mobile devices to begin to document all the cameras they see. I have them take a picture of any surveillance camera they notice during the day. I then have them share these photos with each other, mashing up the data to make a map of all the cameras (http://cameraseverywhere.us/).
With all of these activities, my goal is to have students begin to understand and practice using their mobile devices. And with all of these activities, there are many other ways to accomplish these goals, as well as many other mobile literacies that I think educators need to help students develop. For me, the key piece is recognizing that the mobile computing power in our pockets radically changes not merely our classrooms but, more important, the spaces that students inhabit and the conversations they have outside of our teaching. I want to teach students to take ownership of this type of change so that they can shape the mobile transformation as much as they are shaped by it.
Notes
1. Howard Rheingold, Smart Mobs: The Next Social Revolution (Cambridge, Mass.: Perseus Publications, 2002), pp. xiv, xix.
2. Dean Terry, "Location Literacy & Foursquare in the Classroom," MediaCommons, March 13, 2010, <http://mediacommons.futureofthebook.org/content/location-literacy-foursquare-classroom>.
3. Marshall Kirkpatrick, "How One Teacher Uses Twitter in the Classroom," ReadWriteWeb, June 1, 2009, <http://www.readwriteweb.com/archives/how_one_teacher_uses_twitter_in_the_classroom.php>.

Mengapa 0,999… Sama Dengan 1?

Sejak di Sekolah Dasar, siswa telah diperkenalkan dengan pecahan desimal, bahkan mengenai topik konversi antar bentuk pecahan desimal, persen, dan pecahan biasa. Setiap bentuk pecahan memiliki kelebihan dan kekurangan masing-masing. Oleh karena itu, setiap bentuk pecahan kadang cocok dipergunakan untuk konteks tertentu, namun tidak cocok untuk konteks yang lain. Misalnya ketika berbicara mengenai seberapa besar pertambahan jumlah penduduk, maka pecahan yang paling sesuai adalah bentuk persen.

Dari berbagai bentuk pecahan, pecahan desimal merupakan “bentuk akhir” dari pecahan, karena merupakan implikasi logis dari perkembangan sistem desimal. Seperti yang kita tahu, pada perkembangan sistem bilangan berawal dari pencacahan yang ditandai dengan sistem pengelompokan dan “berakhir” dengan diterimanya secara luas sistem nilai tempat dan sistem desimal (basis 10) menjadi pilihan terakhir umat manusia yang terbukti ampuh penggunaanya baik dalam kehidupan sehari-hari terlebih lagi pada kegiatan ilmiah.


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