How to learn physics?

To learn physics, a positive attitude is a must. And while physics may not be fun, it has many applications in life and work, such as creating life-like reactions in video games, construction and use of heavy equipment, and even driving. This article may help you to overcome your physics trouble.

dark matter

Dark matter is a kind of matter hypothesized in astronomy and cosmology to account for gravitational effects that appear to be the result of invisible mass. Dark matter cannot be seen directly with telescopes; evidently it neither emits nor absorbs light or otherelectromagnetic radiation at any significant level. It is otherwise hypothesized to simply be matter that is not reactant to light.^[1]Instead, the existence and properties of dark matter are inferred from its gravitational effects on visible matter, radiation, and the large-scale structure of the universe. According to the Planck mission team, and based on the standard model of cosmology, the total mass–energy of the known universe contains 4.9% ordinary matter, 26.8% dark matter and 68.3% dark energy.^[2][3] Thus, dark matter is estimated to constitute 84.5% of the total matter in the universe, while dark energy plus dark matter constitute 95.1% of the total content of the universe.^[4][5]

Astrophysicists hypothesized dark matter because of discrepancies between the mass of large astronomical objects determined from their gravitational effects and the mass calculated from the "luminous matter" they contain: stars, gas, and dust. Although based upon flawed or inadequate evidence, dark matter was postulated by Jan Oort in 1932 to account for the orbital velocities of stars in the Milky Way and by Fritz Zwicky in 1933 to account for evidence of "missing mass" in the orbital velocities of galaxies in clusters. Adequate evidence from galaxy rotation curves was discovered by Horace W. Babcock in 1939, but was not attributed to dark matter. The first to postulate dark matter based upon robust evidence was Vera Rubin in the 1960s–1970s, using galaxy rotation curves.^[6][7] Subsequently, many other observations have indicated the presence of dark matter in the universe, includinggravitational lensing of background objects by galaxy clusters such as the Bullet Cluster, the temperature distribution of hot gas in galaxies and clusters of galaxies, and more recently the pattern of anisotropies in the cosmic microwave background. According to consensus among cosmologists, dark matter is composed primarily of a not yet characterized type of subatomic particle.^[8][9] The search for this particle, by a variety of means, is one of the major efforts in particle physics today.^[10]

Although the existence of dark matter is generally accepted by the mainstream scientific community, some alternative theories of gravity have been proposed, such as MOND and TeVeS, which try to account for the anomalous observations without requiring additional matter.

چگونه مساعل فیزیک را حل کنیم؟(انگلیسی)

1

Calm down. It is just a problem, not the end of the world!

2

Read through the problem once. If it is a long problem, read and understand it in parts till you get even a slight understanding of what is going on.

3

Draw a diagram. It cannot be emphasized enough how much easier a problem will be once it is drawn out. Ideally, a free body diagram is what you will draw, but even drawing how you imagine the wording of the problem inside your head (like a chart maybe) will make solving this problem easier. There are often marks awarded for drawing a correct diagram. Once you are done with this, try and bring this drawing into motion like a movie if you can. This is not really necessary but will give you a clear understanding of what is happening in the problem.

4

List down anything that is given to you to the side under a category labeled "known". e.g. you are given two velocities. Label the first V1 and set it equal to the value given. Label the other value V2 and set it equal to the value provided for it.

5

Look for the unknown variables. Ask yourself, 'What am I solving for?' and 'What are the unknown variables in this problem?' List these to the side as well under a category labeled "unknown".

6

List formula that you think might be applicable to this problem. If you are able to look up equations you do not remember exactly and think might be applicable to the problem, do so and write them down

7

Pick the right formula. At times there may be different formulas for the same set of variables and you may be confused as to which one to use. Hence when you memorize the formula, also remember the conditions in which they hold good ( conditions under which that formula can be applied). for example: - v = u + at can be applied only when the acceleration is constant. So in a question if the acceleration is not constant, you will know you are not supposed to use this equation here. This may also help to increase the subject understanding in general.

8

Solve the equations. Take your formula and try to solve for one variable at a time. Solve for each variable that is listed under the "unknown" category. Try to solve for variables that you can determine easily first.

9

Keep repeating the last step for each unknown quantity in turn. If you can't do one, try others first as you may be able to work it out when you have information from other answers.

10

Put a box, circle, or underline your answer to make your work neat

1.