## Thursday, May 5, 2011

### Various Force in This World (II)

Gravitational Force

This is usually called by Newton's Universal Law of Gravity. It is impossible for you who works and study in physics but you don't know about this law. This law was announced in Philosophiae Naturalis Principia Mathematica  or well known by The Principia, Newton's first book about all of Mathematics and Physics law.
And here is the explanation of the law :

Every point mass attracts every single other point mass by a force pointing along the line intersecting both points. The force is proportional to the product of the two masses and inversely proportional to the square of the distance between them.

where :
• F = Gravitational Force between masses ( Newton)
• G = Gravitational Constant (Newton metres2/kg2 )
• m1 = Mass 1 (kg)
• m2 = Mass 2 (kg)
• r = distance between 2 point of masses. (m)
The value of the constant G was first accurately determined from the results of the Cavendish experiment, 6.674×10−11 N m2 kg−2

So, from this law, we know that every single thing which has mass they'll have gravitational force too. Then why we can't feel any force with other things?
Look at the Gravitational constant, the gravitational force will have value 0,00000000006674...Newtons for two things each mass 1 kilo and put in 1 metres distance between their point of mass. So it's so small value. You must have mass as an earth so you can feel it.

## Tuesday, April 19, 2011

### Various Force in This World

• Mechanical Force

1. Gravitational Force
2. Centrifugal/Centripetal Force
3. Coriolis Force
4. Archimedes Force
5. Spring Force
6. Friction Force
etc(I almost forget all of it)

• Non Mechanical Force
1. Electrostatic Force/ Coulomb Force
2. Electromotive Force(emf)
3. Magnetic Force
4. Lorentz Force
5. Atomic Force

etc(I forget it all)

Maybe now I'll mention it. Next, after The National Exams, I'll explain them.

## Thursday, April 14, 2011

### Optical Illusions

AW! Long time not posting here!
Okay today really 4 days to My Final Exam but I decide posting here...hahaha
SO...Let's Go!

1. Circle or Spiral??

2. Are all of this lines parallel?
3. See something strange? A polygon or a cube?
4. What's wrong with this?
5. How many dots do you see?
6. Can you see this picture shifting or moving?

Okay that's enough! See you!

## Thursday, February 24, 2011

### Why Formula 1 Drivers Need a Physical Training too?

Fact

1. Acceleration magnitude : up to 4,5g.
2. Braking decceleration : up to 3-4g.
3. Centrifugal acceleration while cornering : 3g.
4. Heartbeat can beat until 170-180 beat per minute while on the starting grid.
5. Blood pressure until 180-200 mmHg during the race.
First, how big is 4,5g? For example. g is constant gravity where its value is 9,82 metres/second squared.
Still can't imagine how big or how is it feels?
The normal gravity acceleration in equator is g, then, if u deccelerate your motor from 100 km/h to 0 in 4 seconds only, it's just 0.6g. JUST? It's very-very difficult to give a reaction force for its decceleration.

Then, the blood pressure, when in sistolic pressure, it can reach maximum 200mmHg, or 20 cmHg. We know that the standard air pressure is 76 cmHg, it's equal with 100.000 Pa. How big is 20 cmHg?
1 Pa is equal with 1 Newton/metres squared, or maybe you can imagine you are given 1 Newton force in single block with surface area 1 metres squared. It's 1 Pascal/Pa. Then if you calculate 20 cmHg will equal with 26315,... Pa. So you can imagine how big is the pressure inside the blood, or you can find 20 cmHg in the pool. Try to dive until 2 metres from the water surface, with no scuba tools. It's 20000 Pa.

After seeing that facts, we can conclude that the Formula 1's drivers need the physical training to resist them.

## Wednesday, February 23, 2011

### Safety Riding - Medical Physics

Halo
Lama tak berjumpa
Kita kembali kepada Mekanika Klasik, dan kali ini saya tidak ingin memakai Bahasa Inggris soalnya kecampur sama kedokteran sedikit dan aku tidak tahu istilah Bahasa Inggrisnya. Jadi pakai Bahasa Indonesia

Asal  Masalah : Jangan sekali-sekali menyetir mobil dengan lengan hingga telapak lurus menjadi 1 garis!
MENGAPAAA??
Mulai dibahas satu-satu

Pertama.
Coba kalian luruskan tangan kalian sampai selurus-lurusnya, perhatikan siku kalian dan sendinya. Membentuk sudut 180 derajat atau tidak? Believe it or not, itu bukan 180 derajat. Kurang dari 180 derajat, alias bengkok ke arah luar. Jika kalian berdiri tegak dan tangan kalian diluruskan, pasti akan membengkok menjauhi tubuh kita. Kalau tidak terlihat, lihat pakai X-Ray!

Kedua.
Apa pengaruh tangan bengkok dengan safety riding?
GAYA FIKTIF! Jika kalian tiba-tiba mengalami kecelakaan fatal, mungkin KEPALA anda bisa terselamatkan dari setir mobil, tetapi, bagaimana dengan tangan anda? Lengan anda? Terutama bagian Radius,Ulna dan Humerus Gaya fiktif tersebut mempengaruhi gerakan kedua tulang tersebut jika terjadi kecelakaan mendadak. Jika tangan kalian menekuk saat menyetir, kemungkinan terjadinya patah dan dislokasi akan lebih kecil dibandingkan dengan sangat lurus.
Jika tidak percaya, praktekan dengan ekstra hati-hati. Bandingkan lebih nyaman bagaimana, mendorong sebuah mobil dengan tangan menekuk atau lurus, jika lurus akan sangat sakit dibagian siku pasti.
Sama saja halnya dengan yang terjadi saat kecelakaan, gaya fiktif tersebut sangat besar karene perubahan momentum yang juga besar, dan massa kalian yg sangat kecil dibanding mobil, tentu saja kekuatan sendi tersebut akan menjadi SANGAT SANGAT KECIL. Jadi, usahakan menyetir dengan tangan menekuk!!

FYI: This is the first time I post about Medical Physics

## Thursday, February 10, 2011

### Time is Important!! -> World Activity

Hei all! Long time no post huh? Okay. Let's talk about time now. This is the topic I'll talk now. And I think it's about the high speed part(again)

So we'll talk how important is 1 minute, 1 second, 0.1 seconds, 0.01 seconds, 0.001 seconds until 0.000 1 seconds.
First, 1 minute.
I think it doesn't make any sense with 1 minute, because if we fall asleep in 1 minute, I think we only left by an accident or what. I don't know. You can write it down by yourself about one minute.
Second, 1 second.
Okay this is become important if you're driving a car in highway. You know, we can drive till 30 m/s, converted in km/h it becomes 108 km/h. Yes, if we turn our head just in 1 second. It's possible that 30 metres in front of us a car get damaged and stop suddenly. Okay, 1 second become a great accident. Imagine, from the initial velocity 30 m/s you stop instantly. Maybe you'll rest forever and ever in HEAVEN.
Next, 0.1 seconds.
You know football? Absolutely. In penalty kick, if the goalkeeper miss 0.1 seconds, he can left behind by the ball and it can turned into a big lose. The average speed of football ball is  97 km/h. It's 26 m/s. So count it if the goalkeeper missed 0.1 seconds, it's 2.6 metres left. I think the ball has already got inside the goal.
Next 0.01 seconds
The badminton player should pay their attention for this one. The shuttlecock are running in 300 km/h, they are very fast, like a bullet, so if they miss 0.01 seconds, the enemy smash could make the enemy won the game.
1 milisecond.
It's important for the sprinter, they can turned from gold medal into silver medal by miss 1 miliseconds.
0.000 1 seconds.
The Formula 1 projects with cost about US\$ 6 868 000 can turned into a 'trash' because they miss 0.000 1 seconds. This landjet contest are very-very worth. The winner and the runner up can adrift just by 0.000 1 seconds.

I think that's all for the first Time post.

## Saturday, January 22, 2011

### Mengapa Fisika itu Sulit

Saya habis membaca di internet, beberapa pertanyaan tentang cara belajar fisika, unik-unik juga rupanya. Ini dia beberapa diantaranya:

1. Mengapa fisika itu sulit?
2. Mengapa fisika itu banyak rumusnya?
3. Mengapa fisika itu materinya banyak sekali?
4. Mengapa model-model soal fisika itu banyak?
5. Mengapa aku punya teman yang suka fisika?
6. Mengapa aku punya teman yang jago fisika dan mudah sekali membuat soal fisika?
7. Kenapa kuliah teknik mesti ada fisikanya?
8. Kenapa aku selalu gak bisa fisika?
9. Dan yang paling menyinggung : Mengapa aku sekelas sama anak Olimpiade Fisika?????

Yah memang lucu-lucu dan bermacam-macam menurut saya. Tetapi jujur, fisika itu tidak akan sulit jika kita bisa membayangkannya di dunia nyata. Itu adalah salah satu kunci utama untuk mengerjakan soal fisika. Baru kita bisa mengambil konsep-konsep yang kita pelajari. Memang banyak materi dalam fisika, tetapi, intinya hanya beberapa. Saya pernah membaca sebuah artikel bahwa ada seseorang fisikawan yang berhasil merangkum seluruh hukum fisika secara utuh hanya dalam 3 lembar kertas folio. Yang hanya terdiri rumus dasar, dari fisika dasar hingga kompleks, dari fisika klasik hingga modern. Terbukti bukan? Bahwa fisika itu tidak seperti pertanyaan-pertanyaan diatas.