Astronomi

Astronomi, yang secara etimologi berarti "ilmu bintang" (dari Yunani: άστρο, + νόμος), adalah ilmu yang melibatkan pengamatan dan penjelasan kejadian yang terjadi di luar Bumi dan atmosfernya. Ilmu ini mempelajari asal-usul, evolusi, sifat fisik dan kimiawi benda-benda yang bisa dilihat di langit (dan di luar Bumi), juga proses yang melibatkan mereka.

Selama sebagian abad ke-20, astronomi dianggap terpilah menjadi astrometri, mekanika langit, dan astrofisika.

Astronomi ialah cabang ilmu alam yang melibatkan pengamatan benda-benda langit (seperti halnya bintang, planet, komet, nebula, gugus bintang, atau galaksi) serta fenomena-fenomena alam yang terjadi di luar atmosfer Bumi (misalnya radiasi latar belakang kosmik (radiasi CMB)).

Ilmu ini secara pokok mempelajari pelbagai sisi dari benda-benda langit seperti asal-usul, sifat fisika/kimia, meteorologi, dan gerak dan bagaimana pengetahuan akan benda-benda tersebut menjelaskan pembentukan dan perkembangan alam semesta.

Astronomi Bulan: kawah besar ini adalah Daedalus, yang dipotret kru Apollo 11 selagi mereka mengedari Bulan pada 1969. Ditemukan di tengah sisi gelap bulan Bumi, garis tengahnya sekitar 93 km

Astronomi adalah salah satu di antara sedikit ilmu pengetahuan di mana amatir masih memainkan peran aktif, khususnya dalam hal penemuan dan pengamatan fenomena sementara. Astronomi jangan dikelirukan dengan astrologi, ilmusemu yang mengasumsikan bahwa takdir manusia dapat dikaitkan dengan letak benda-benda astronomis di langit. Meskipun memiliki asal-muasal yang sama, kedua bidang ini sangat berbeda; astronom menggunakan metode ilmiah, sedangkan astrolog tidak.

1 Astronomi observasional

• 1 Astronomi radio
• 2 Astronomi inframerah
• 3 Astronomi optikal
• 4 Astronomi ultraungu
• 5 Astronomi sinar-X
• 6 Astronomi sinar-gamma
• 7 Cabang-cabang yang tidak berdasarkan panjang gelombang
• 8 Astrometri dan mekanika benda langit

2 Astronomi teoretis

3 Cabang-cabang spesifik

• 1 Astronomi surya
• 2 Ilmu keplanetan
• 3 Astronomi bintang
• 4 Astronomi galaksi
• 5 Astronomi ekstragalaksi
• 6 Kosmologi

Sumber:

Wikipedia.

Fisika SMA

Pengalaman Belajar Fisika di SMAN BI 1 Banjar

Ada Apa Dengan Fisika

Experiment: Vector Addition by the Numerical Method

SUBJECT: Mathematics
TOPIC: Vector Addition
DESCRIPTION: A set of problems dealing with vector addition.
CONTRIBUTED BY: Carol Hodanbosi
EDITED BY: Jonathan G. Fairman - August 1996

Purpose:

A vector is a quantity that has both magnitude, or size, and direction. Forces can be represented by vectors, since they have both a size and direction of action. Below is an example of a mass supported by two cables. If the mass is not moving, all the forces acting on the mass are considered to be balanced. You will investigate each of the forces acting on the mass and compare their relationships.

Fw represents the weight of the object. It is found by mulitplying its mass by gravity. That is, Fw = m * g, where g equals 9.8 m/s². This force is directed downward.

Exercises:

1. If the object represented by F has a mass of 4.8 kilograms, find its weight.
   (answer)
   
   
2. What direction is the weight of the object acting? Draw this vector through the center of mass of F .
   (answer)
   
   
3. 
   
   The lines CB and CA are vector quantities that are supporting and acting opposite the object F . Draw a line through point C parallel to the base support. Measure the angle between CB and the line just drawn.
   Since vectors CB and CA are not acting parallel or perpendicular to the base of the stand, it is helpful to find the components of each of these vectors. Components are vectors that combine vectorally to form the resultant vector, in this case CB or CA . For example, to find the components of CA or CB one first needs to find the angle that vector forms with the horizontal line, angle ACD or angle BCE , see diagram below.
   
   
   
   
   
   To find components of vector CB , form a right triangle with CB as the hypotenuse. Since CB is a vector, or a ray, one will be selecting a fixed portion of CB . Recall the trigonometric functions of the sine (side opposite/ hypotenuse) and the cosine (side adjacent / hypotenuse). The sine of angle BCE would equal side BE/CB , while the sine of angle ACD = AD/ AC .
   Let's assume that the angle ACD and angle BCE are both 35° and that the weight represented by vector CF is 100 newtons. Since the weight is static, and not moving, we can assume all the forces are balanced. The vector represented by CE (to the right) must be balanced by the vector CD (to the left).The downward force of the weight represented by CF must be balanced by the two upward forces DA and EB . Since the two right triangles have two congruent angles (35°) and two congruent sides, (FD and CE ) the two triangle are congruent (Leg, Acute angle).
   Because DA + EB = CF then DA = EB = 50 newtons.
   
   By substitution, Sin angle BCE = BE/CB
   
   
   Sin 35° = 50/CB
   CB = 50 /Sin 35°
   CB = 87.17 newtons One can also find the measure of CE or CD using the tangent function.
   tan BCE = BE/EC
   tan 35° = 50 /EC
   EC = 50 /tan 35°
   EC = 71. 4 newtons
   
   
   Now use the following diagram to solve the problems below.
   A load of 500 kg is suspended at the end of a horizontal boom supported by a cable. The cable makes a 42° angle with the boom and is attached to a wall by a supporting pin. You can assume the boom's mass is negligible.
   
4. Find the downward force vector (the weight of the mass).
   (answer)
   
   
5. Represent the components of the cable (one is inward toward the wall, the other is upward, opposite the mass).
   (answer)
   
   
6. Find the tension in the cable.
   (answer)
   
   
7. Find the outward force of the boom.
   (answer)
   

Sumber:

NASA

Fisika SMA

Ada Apa Dengan Fisika?

Pengalaman Belajar Fisika di SMAN BI 1 Banjar

Belajar di Sekolah Bertaraf Internasional

To better understand the science of propulsion it is necessary to use some mathematical ideas from vector analysis. Most people are introduced to vectors in high school or college, but for the elementary and middle school students, or the mathematically-challenged:

DON'T PANIC!.

There are many complex parts to vector analysis and we aren't going there. We are going to limit ourselves to the very basics. Vectors allow us to look at complex, multi-dimensional problems as a simpler group of one-dimensional problems. We will be concerned mostly with definitions The words are a bit strange, but the ideas are very powerful as you will see.

Math and science were invented by humans to describe and understand the world around us. We live in a (at least) four-dimensional world governed by the passing of time and three space dimensions; up and down, left and right, and back and forth. We observe that there are some quantities and processes in our world that depend on the direction in which they occur, and there are some quantities that do not depend on direction.

For example, the volume of an object, the three-dimensional space that an object occupies, does not depend on direction. If we have a 5 cubic foot block of iron and we move it up and down and then left and right, we still have a 5 cubic foot block of iron.

On the other hand, the location, of an object does depend on direction. If we move the 5 cubic foot block 5 miles to the north, the resulting location is very different than if we moved it 5 miles to the east. Mathematicians and scientists call a quantity which depends on direction a vector quantity.

A quantity which does not depend on direction is called a scalar quantity.


Sumber:

http://www.grc.nasa.gov/WWW/K-12/airplane/vectors.html