Physics problems are easy!
General rules for formatting problems in physics
(valid for all ages of students “from young to old”, as well as applicants, when solving any type of problem!)
To correctly solve any problem, do not forget about the mandatory rules for formatting the solution to these problems.
More than once the teacher reduced your grade for a paper just because you wrote down the solution incorrectly.
Well-learned rules will help you not get confused in the most basic things, and, in addition, it will have a decent appearance in the eyes of the inspector!
1. So, carefully read the terms and conditions tasks and figure out what topic this task is about, i.e. what quantities are we talking about, what physical processes are considered in this problem.
Sometimes, without paying attention to one single word in the conditions, you will not be able to further solve the problem!
2. We write down brief conditions in the left column under the word “Given”, first the letter designation of the physical quantity, then its numerical value.
note, sometimes some data is written in the condition not in numbers, but in words. For example: water at a boil... Remember the boiling point of water under normal conditions and write it down as +100 degrees Celsius.
Always leave free space in this column, because during the solution process you may need additional background information that you did not even suspect at first.
Record numerical data with units of measurement. This is a mandatory requirement when solving physics problems!
If the unit of measurement is a fraction, write it only with a horizontal fraction bar. How many times has such a correct entry helped to avoid mistakes!
Decide what needs to be found in the problem, and write down the letter designation of this physical quantity under the word “Find”. The inspector will not do you any favors if you calculate a different value! In this case, the task will not be counted!
“What unnecessary subtleties!” you are thinking now. But the time of the test or exam will come, and they will serve you well!
3. Usually the problem is solved “in the SI system”.
Don't forget to highlight the column next to the brief terms to convert units into the SI system (even if this is not required in this problem).
Difficult translations can always be made in writing in the decision.
Well, are you ready to solve the problem?
4. There are problems whose solution unthinkable without a drawing!
For example, motion problems: coordinate axis, velocity vectors, acceleration, displacement, acting forces... Often it is the drawing that allows you to understand such a problem.
And even if the task is not about movement, a drawing for the task will help you.
5. And now directly write down the solution!
In physics, any calculation must be preceded by writing a formula, and all quantities in the solution must be written with units of measurement.
There are two ways to solve the problem:
A) decide by actions;
b) solve in general form, that is, draw the final formula, and then one final calculation. Such a decision is “aerobatics” for students in grades 7-9, and for high school students it is simply a must!
But if it was not possible to solve the problem in general, then at least in terms of actions... It will still be solved!
Sometimes the solution to a problem is obvious to you, and sometimes you don’t know “from which end” to take on it. In the second case, unwinding the solution from the end helps. Think about what you need to know to calculate the required value? And solve the problem as if in the opposite direction. It will definitely work out!
OK it's all over Now?
Nope!
6. Required check the answer!
First, "for the fool"!
What if your fly in the problem flies at the speed of a rocket?
What if your submarine weighs only a few grams?
And finally, write down the word “Answer” and the calculated value next to it, not forgetting to indicate the units of measurement.
OK it's all over Now!
But nothing new!
Not so difficult for those who want to learn how to solve problems without mistakes!
First, gather your courage, keep in mind that it will take time to learn how to easily solve problems at your current level of knowledge and intelligence. The main thing in solving physics problems is regularity. You have to do them every day.
Step 2
Now to the point: now I’ll write a slightly strange and obvious phrase, don’t think that I’m an idiot. To easily solve problems of a certain level of complexity, you need to learn how to solve even more complex problems. Let me give you an example: there are school problems, Olympiad problems, problems from the Unified State Exam in Part C, and, finally, the most difficult ones - problems from Irodov’s problem book, which is currently the most difficult textbook.
Buy or download textbooks for grades 10 and 11 in physics (“Classical Course” publishing house education), Savelyev’s textbook “Course of Physics. Mechanics. Molecular Physics.” is his first volume, and necessarily Irodov’s TEXTBOOK, also the first volume.
Step 3
Read grades 10 and 11 in full.
Buy or download problem books by Chertov, Irodov and problems from the Unified State Exam.
Step 4
Well, start solving Chertov’s problems - the problem book is quite simple, just know the formulas and substitute them. There should be no problems, solve problems from kinematics, try to solve more, if suddenly you can’t solve the problem, look for a solution on the Internet, read it carefully, it is important to understand the principle of solving the problem. After that, you again solve the same problem that you were unable to solve; if you really understand how it is solved, then you will solve it without problems.
Step 5
It’s exactly the same with problems from the Unified State Exam. Now the hard part is Herodov. Before opening his problem book, be sure to read Savelyev, then the manual of Herodov himself. Next, open Irodov’s problem book and go ahead, try to solve problems using the same kinematics, start from the very first one. The first one is quite simple (it’s in the photo). Write your answers to the first problem in the comments, if no one solves it correctly, I will write the correct answer, if you are very interested in how it is solved, write in private messages and I will explain.
Step 6
I guarantee that as soon as you learn to solve most of the problems from Herodov, any other problem book will seem very simple to you!!!
I used kinematics as an example; this applies to all other sections to exactly the same extent.
This small instruction is valid for problems in any section of physics: dynamics, kinematics, electrodynamics and any others. In addition, in order to solve a problem correctly, you need to remember the rules for formatting a solution. It may happen that the teacher simply does not understand your decision. The rules described below will help you not to get confused in simple things when solving problems in physics.
1. Carefully read the terms of your physics problem. Figure out what topic the problem is about, what, in general, it is about - the dynamics of temperature changes, or the force of friction - in general, what physical phenomena and processes are considered in the version proposed to you. Remember that every word in the condition plays an important role!
2. Write down brief conditions, this will be familiar to everyone from the “Dano” school. It must be written briefly: the letter of the quantity designation and its value from the condition. Don't forget about units of measurement! You also need to remember that the condition of a physics problem may contain “hidden” data. For example, the phrase “water is boiling in a cauldron” means that you need to record the boiling point of water as the initial data. That is, in the “Given” section write tk = 100o C. Don’t forget about what you need to find. This unknown quantity is written in the “Find” section.
3. Remember the SI system! It often happens that the problem conditions are indicated in units of measurement other than SI. This usually leads to nonsense in the answer, and the opinion that the decision is wrong - although it just turns out to be correct!
4. Drawing. A number of problems cannot be solved without a schematic drawing. These include motion tasks - various movements of rigid bodies, accelerations and inclined planes with blocks and threads. In general, a drawing helps to better understand the essence of a problem, physical process or phenomenon. They often lead to the right decision!
Thus, the important stage of preparation for the decision is completed.
5. It's time for a decision! There are also several important rules here. The first of them is that before any numerical calculations it is necessary to write a formula. Also, remember to write all units of measurement so as not to “lose” anything in the final answer.
6. You should be aware of the approaches to the solution. The first option is to solve the problem step by step - calculating the digital answer for each formula. This option is not preferred and is used very rarely. The second option is a solution in general form - derivation of the final formula, and only then a numerical calculation.
7. If you have absolutely no ideas on how to approach the solution, try starting from the end. Think about how to calculate the quantity you want to find, and then see what is missing to calculate it. Often this approach helps.
8. Don't forget to check the answer! First, based on simple logic - for example, a car cannot travel at escape speed, and an airplane cannot weigh a couple of grams. Also, be sure to include the units of measurement for your answer.
That's all, a small instruction on solving physical problems is completed.
Of course, it will seem to you that this will not help in solving in any way - but we hasten to assure you that this is the only way to learn to solve problems in physics! Unfortunately, there is no magic instruction that can be used to solve any problem immediately and in 5 seconds.
(In this section we plan to post tips and recommendations for schoolchildren who want to learn how to solve problems in physics. Therefore, if you have questions of a general theoretical nature, if you would like to clarify something, feel free to ask in the comments. If necessary, we will write another article , and not just one.)
It should be remembered that physics problems in models reflect physical reality the surrounding world. When starting to solve the next problem, even the simplest one, try to recognize the phenomenon imagine it in your mind, discuss its progress (if you have someone), and only then begin to search for an answer to the question posed in the task.
If it is difficult for you to imagine how a physical phenomenon occurs, try looking at interactive physics models. This is a flash animation that helps to better understand the essence of the phenomenon and simulate it under different conditions.
- You can formalize the task traditionally:
- short description of the condition, where it is necessary to reflect not only these numerical values, but also all additional conditions that follow from the text of the problem (although this is not always obvious, but arises during the solution). The constancy or multiplicity of any parameters, their boundary values, conditions that are determined by the physical content of the problem (for example, absence of friction, constancy of acceleration, etc.).
- drawing up a task: make a drawing for the task that displays the situation described in the task, plot all the given conditions of the task, and formulate the question of the task.
The drawing is especially necessary if the equations used are given in vector form. In this case, it is necessary to draw a coordinate system, relative to which the vector equation should be written in projections. Drawing in most cases greatly simplifies the decision process any problem, not only in physics.
The drawing is also necessary if the body is moving or located at an angle.
- Very important correctly pose the question to the problem. The following options are possible:
- the question of the task is formulated clearly and understandably, for example, find the value of a parameter(there are no difficulties when posing such a question);
- by how much or how much one quantity differs from another. Here you need to find the difference between two values of one parameter (speed, force, etc.) or find the ratio of physical quantities.
Example: HOW MUCH did the speed increase? Change speed = final speed minus initial:
Be careful!Another example: HOW MANY times did your body weight decrease? Need to find out:
- if the question is: “ How did any parameter change?", then you need to choose FOR HOW MUCH or HOW MUCH (how many times..?) depending on the task data. If the change is relatively small, choose for how long. If the parameter may differ several times, it is better to choose how many times.
In answer to the question " How has it changed? speed.. ?" always subtract the initial value from the final value:
Moreover, if the speed increased, then:Practical conclusion: if the speed increased and you got ΔV< 0, хорошенько задумайтесь. И наоборот.
- It is necessary to check whether all given quantities in the problem are in the same system of units (SI, CGS and others). If quantities are given in different systems, they should be express in units of the system you adopted for the solution. The SI system is preferred, but not always.
So, the condition of the problem is formalized, now you can start solving the problem.
- We are thinking about it physical content of the problem, we find out which section it belongs to, and what laws should be used in it. Problems can be combined; their solution requires the use of the laws of several branches of physics. In problems of mechanics, usually the first question that must be asked is: what is the nature of the movement?
- Followed by write down formulas corresponding to the laws used in the problem, you should not immediately look for an unknown quantity; you need to see if all the parameters in the formula are known. If the number of unknowns is greater than the number of equations, it is necessary to add equations following from the condition and figure. General principle: how many unknowns there should be so many formulas. Then all that remains is to decide system of equations, that is, to reduce the problem from physical to mathematical.
An example of such a task:
An observer standing on the platform determined that the first car of the electric train passed him within 4 s, and the second - during 5 s. After this, the front edge of the train stopped at a distance 75 m from the observer. Assuming the motion of the train to be uniformly slow, determine its acceleration.
This task (in a slightly different form) was posted in the section Let's decide together. It is solved by composing a system of 3 equations. Try to solve it yourself; if you can’t, look for a solution on our portal.
- Common mistake: incomplete understanding of the meaning of parameters in the formula. Schoolchildren are quite capable of solving a physics problem, but they often get confused in their notation.
An example of a real problem that turned out to be difficult for a 10th grader:
The athlete ran 100 meters behind 10 Seconds, of which 2 seconds he spent on acceleration. The rest of the time he moved evenly. What is its speed of uniform motion?
The problem with the solution here arose because the schoolgirl got confused in her notation: 10 s, 2 s, 8 s. If you don’t think through the notation, you can spend hours on this simple task. By the way, the problem has 2 ways to solve: analytical (formula) and graphical.
- The solution to the problem most often should be performed in general, that is, in letter designations.
- The solution "by action" may not work, since some unknown side parameters may can be reduced only when solved to the end in general form.
- Another reason for the general (literal decision) is that when deciding on actions, final result error that, especially in tests, can do a bad job. And he solved the problem, but chose the wrong answer. Therefore, you should not be afraid to enter parameters that are not included in the problem statement. If the transformations are very cumbersome, then you can make intermediate numerical calculations, while trying to avoid rounding, and leave in fractions Thus, errors will be avoided.
- Having received the solution in general form, you need to check dimension of the obtained value. To do this, substitute not numbers into the formula, but the dimensions of the quantities included in it. The answer must correspond to the dimension of the desired quantity, this is a guarantee of the correct solution of the problem. After checking the formula for dimensionality, you should substitute the numerical values of the quantities included in it and make a calculation.
Dimension check example. Solving a problem that asked about the tension forces of a thread (measured in N), we received the following response:
Indeed, we have obtained the dimension of force. The question may arise: what if I don’t remember the dimensions? w And F? There is a way out, but verification is a little more complicated. Remember the basic formulas: w = 2πν, Where ν is the number of full revolutions per second, so the dimensions w And ν match up. Second formula: F = ma, having written the dimensions included in it, you will see that 1 N = 1 kg.m/s 2. Q.E.D.
You should check the size after long complex transformations where it's easy to make a mistake. Based on different dimensions, you will quickly see the wrong answer, but (note!) the dimensions coincide does not guarantee that the task is solved correctly.
- Next you need to analyze and formulate an answer. If the question was “how has it changed...”, then you need to indicate direction of change(increased, decreased, slowed down, etc.)
That's all, the problem is solved. Good luck!
P.S. We advise you to regularly solve physics problems. Athletes, preparing for competitions, train several times a day. Get started solve problems daily and after a while you will feel that you can solve each subsequent task faster and with less effort. You will learn to “see” them from the inside even without a drawing. But this skill is being developed only regular training. The ability to quickly solve problems is useful not only when passing exam tests, but also when studying at a university. Verified. That's why: Not a day without a solved problem!
We all encounter solving problems in physics at some point. And I must admit that for most of us this is not the most long-awaited meeting. However, we know that just a few simple steps and simple actions will allow you to get on the same page in your relationship with Physics. Problem solving is an important part of the learning process that should not be underestimated. After all, solving physical problems on various topics brings the understanding of physical processes to a qualitatively new level.
If you have never encountered problem solving before, a reasonable question arises: where to start?
How to solve physics problems
So that solving problems in physics does not cause difficulties, we suggest following when solving any tasks of the following universal instruction. It doesn’t matter at all whether you need to solve a motion problem or find out how much heat Q will be released during an isobaric process. This instruction will not provide an answer to a specific problem, but it can make its solution simpler and faster.
- Don't rush and don't panic! Remember the first rule of the Galaxy Guide: “Don’t panic.” As a rule, the standard tasks of most courses are solved in one or two (okay, three) steps, and there is nothing overly complicated in them. First of all, carefully read the problem statement and understand what you need to find in it. Check out similar examples of solving problems in physics.
- Now you can register “DANO” . Carefully write down all the given values and do not forget about the dimensions. It is advisable to immediately convert the dimensions of quantities into the SI system, so as not to get confused in the calculations later.
- Very important point: FIGURE . Yes, we are not Picasso or Dali, but our artistic abilities will be quite enough. A correct explanatory drawing for a problem is the key to success and the right solution. Data visualization helps a lot and should not be underestimated. Remember, in physics problems something is always happening - a puck flies at an angle to the horizon, an electron bombards a plate, an ideal gas does work, a father and son change places in a boat, and so on. So, don’t be lazy and draw it! And not just like that, but with an indication of the acting forces, velocity vectors and other data in the problem of quantities.
- Now that the whole picture is before our eyes, You should understand what physical law the solution to your problem is based on. Often this can be found out purely intuitively. If the problem concerns a body that moves in a circle, and you need to find the moment of inertia, obviously this is a problem using the laws of the dynamics of rotational motion. Or if the path and time are given, but you need to find the average speed - this, of course, is kinematics. It may be useful to study the corresponding section of physics again immediately before solving the problem.
- The time has come to think about how exactly to find the desired value, knowing what we actually know. For convenience, you can place physical formulas in front of your eyes. This will help you quickly figure out what is coming from where and where it is located. A little brain work and bingo! You already know what to do next.
- It is advisable to first write the solution in general, literal form. The formula with letters should be brought to the simplest possible form, simplifying it if possible. After this, you can substitute numerical values and proceed directly to calculations. At the end, do not forget to check the dimension of the resulting physical quantity. If you needed to find the speed, but you got kilograms, it means there was an error hidden somewhere in the solution. Be careful and everything will work out!
Of course, it also happens that you have to sweat over a task. There are nuts that cannot be cracked the first time, especially without the proper experience. Are you trying your best, but the solution is still not given? The main thing is never give up! Just look at Nikola Tesla and it will give you the strength to try again and again!
By the way! There is now a discount for all our readers 10% on .
The flywheel made 8 revolutions per second. Under the influence of a constant braking torque of 10 N*m, it stopped after 50 seconds. Determine the moment of inertia of the flywheel.
So let's begin the solution. You need to find the moment of inertia - a scalar physical quantity that is a measure of the inertia of a body in rotational motion around an axis. Let's write down the given data, draw a flywheel, and understand that the problem must be solved using the basic equation of the dynamics of rotational motion, according to which the resulting moment of the external force acting on the body is equal to the product of the moment of inertia of the body and its angular acceleration. We obtain a solution to the problem in the following form:
We hope that our universal and time-tested guide to solving physics problems will be useful. After all, the best authors in physics use it to solve problems of any complexity. Of course, each task may have its own twist, and it is worth remembering that an individual approach to a task is an important component of success and understanding of the subject. However, all the items we have given on the list are truly suitable for solving any problem. Well, if you have any questions, feel free to ask them to the student service specialists, they will be happy to share their knowledge!
