Brief rules

  • Online Physics Brawl is a three-hour-long team competition happening over the Internet.
  • The competition is mainly intended for high school teams of up to 5 students.
  • The competition includes Open category where anyone can participate.
  • Participating teams compete in solving short physics problems. The solution to every problem is a number that is sent to our servers using a web form.
  • Teams are awarded points for successfully solved problems. During the competition, the score of each team is visible to every other team until 20 minutes before the end. At that point, the scores are hidden and not shown to the participants again until the competition finishes.

Full version of rules

Full version of rules

Official announcements by the organizers will be posted to the noticeboard during the comperition. Players have to follow this noticeboard.

There is a change in rules of Hurry-up part compared to previous years. We also merged czech high school categories with foregin high school category.

Basic information

  • Teams consist of 1–5 players.
  • Every team is a member of one of the following four categories based on team coefficient. Team coefficient is the average value of player coefficients in the team. Each player has a player coefficient based on the expected year of graduation (ISCED 2011 level 3). If a player is studying his last year, he gets a coefficient of 4. If he is studying the penultimate year, he gets a coefficient of 3 and so on... A minimum possible coefficient is 0.
    The categories are as follows:
    • C – team coefficient ≤ 2 & no member of the team has a player coefficient of 4 & a maximum of two members has a player coefficient of 3
    • B – team coefficient ≤ 3 & a maximum of two members has a player coefficient of 4
    • A – team coefficient ≤ 4
    • open – everyone who cannot or does not want to be in the high school categories.
  • Teams solve the same problems no matter what category they are in. Winners of each category will be announced separately. Absolute winners will be announced as well.
  • Participation in the competition is free.
  • The award for the best teams is the eternal fame and prestige gained by winning a competition like this.
  • Collaboration among different teams is not allowed.
  • While we do monitor the competition and can uncover some methods cheating we still mainly rely on trust in your sportsmanship. We assume all the teams participate because they want to have fun competing. Cheating will spoil this purpose.
  • All members of the team agree with processing their personal information by registering into the competition. Your information will be used for appraisal of the competition and its improvement.


  • There will be more than 60 problems in the competition. The precise amount of problems is different every year and is not released ahead of time.
  • Problems will be available on the web of the competition in the form of a PDF file. You will need your team's password to access the problems.
  • The answer to a problem is always a number that is delivered via a web form. Unless otherwise stated, you should assume that this number is real. The minimum number of significant digits we expect you to write down will be stated in each problem. Check this before submitting your answer! You do not need to worry about numerical inaccuracies, rounding up etc. since each problem will have a range of correct answers.
  • If there is a numerical value of a certain constant in the problem statement, you should use exactly this value in your calculations.
  • Unless otherwise stated, answers should be expressed in the base SI units. Examples:
    • A train is moving at a speed of 50 km/h. What is the distance it travels in a minute? State your answer to at least 4 significant digits. — for example 833,3 or 833,33 are both correct answers (the unit is not specified and the answer should therefore be in SI base units)
    • A train is moving at a speed of 50 km/h. How many kilometers will it travel in a minute? One significant digit is enough. — for example 0,8
    • How many carbon atoms (an integer) does a single molecule of a cyclopentano-perhydrophenanthrene contain? — the answer is 17 — 17,0001 is a wrong answer
  • The competition will consist of a large spectrum of physics problems. Some of them will be very easy and some of them really hard. Therefore, different problems will be worth different amounts of points. Easier problems will be in the so-called Hurry-up series. However, you will have much more limited amount of time to solve them.

Rules and the scoring system

  • The competition comprises two parallel parts, the Major contest, and the Hurry-up series.
    • Major contest: 17:00 - 20:00 (UTC + 1)
    • Hurry-up series: 18:00 - 20:00 (UTC + 1)
  • The competition lasts 3 hours and will end at 20:00.
  • In both, Major contest and Hurry-up series, each team will be given a specific number of problems to solve. Once a team solves a problem, it will gain access to the following one (in the appropriate contest).
  • At 18:30, teams will be enabled to skip unsolved problems. This action will be penalized by 1pt and the team acquires access to the following problem instead.
  • If a team skips a problem, it will no longer be able to submit an answer to it.
  • Each team can skip a maximum amount of 10 problems.
  • Teams are awarded points for correct submissions. Each problem is assigned a number of maximal points you can earn by solving it.
  • Contestants can submit an answer to a problem as many times as they wish. However, teams can earn the maximal amount of points only if they answer correctly with their first submission. With each wrong answer, the amount of points the team can earn decreases (see Major contest, Hurry-up series).
  • If a team answers incorrectly, it will not be able to submit any answers for 1 minute (in the appropriate group of problems, i.e. major contest or one of three hurry up groups).
  • If two teams happen to end up with the same score, the team which solved their last problem earlier will be prioritized.
  • The preliminary results are revealed immediately after the contest, the final standing are announced after half an hour.

Major contest

  • In the Major contest, each team will be given the first 7 problems. Once a team solves a problem, it will gain access to the following one. There are approximately 50 problems in this section.
  • The maximal amount of points for each problem varies from 3 to 9 based on its difficulty.
  • If you answer correctly the first time, you get the maximum amount of points. If you need one more try, you will only gain 0.6 times the maximum number of points. If you need three attempts, you will get 0.4 times the maximum and if four, it is 0.2 times the maximum. However, no matter how many times you try to answer a problem, you will always get at least one point. The amount of points you get is always rounded up.

Hurry-up series

  • An hour after the beginning of the competition, teams will be enabled to answer the problems in the so-called Hurry-up series.
  • The problems are divided into three groups according to their topic (mechanics M, electromagnetism E, other X).
  • When the Hurry-up series is launched, teams are given one problem from each of the aforementioned groups. Correctly answering a problem will grant you access to the next problem in the same group (after a correct answer to M.1, problem M.2 is unlocked).
  • The Hurry-up problems are easier (usually worth 3 pts).
  • If you answer a problem from the Hurry-up incorrectly, the possible amount of points you can get for this particular problem decreases in the same way as major contest. Therefore, unlike the problems in the major line, you can get zero points (but no negative points) for a problem in the Hurry-up series.
  • If you correctly answer three problems so that each of them is from a different group, and they all have the same sequence number in their corresponding group (e.g. M.1, E.1, X.1) during the first half an hour of hurry-up line (18:00 - 18:30), the points received from this triplet of problems are doubled.
  • The hurry-up problems are still available after 18:30, but you do not get the bonus points for completing a triplet.

What do I need to have to participate?

  • Access to the Internet (the speed of your connection should not matter). More than one device with access to the Internet is an advantage but it is not necessary. You are allowed to use the Internet as a source of information that can help you solve the problems. (You are not allowed to use it to communicate with people outside your team about the problems.)
  • A printer is not necessary but it might be helpful.
  • Papers, pens, literature, calculators, …
  • Snacks.
  • Team mascot.


  • Having more people in your team is an advantage. Therefore, we recommend that you have all of the five positions filled.
  • It is important to decide on a strategy to attack the problems. What problems can you do quickly? Is it better to work as a team or to divide the work among individual members? Who decides what individual members work on? You will have a lot of problems available during the competition so it is an advantage to know how to approach them as a team beforehand.
  • During the competition you will be able to see how other teams are doing as well as the statistics of each problem. This will end 20 minutes before the end of the competition. Use this information to figure out what problems might be easy or hard.
  • We suggest occasionally watching the forum for new information as well. If you don't understand a problem, maybe somebody else has already asked for a clarification there — and it's faster to read the answer than ask the same question again!


  • Besides the non-fading glory you can win diplomas, T-shirts, hoodies or flash drives.
  • First three teams in categories A, B, C and the overall winner (including open category) will be rewarded.

Code of honour

  • Even though we believe that the following will never have to be used we still need to include it. The organizers reserve a right not to let a team sign up, continue in participating or even deleting it from the scoreboards in the case that fair-play shall be disrupted in some way by said team or if some detestable behaviour is detected in connection with the competition.
  • Namely (mainly but not limited to): if the submitted personal data are false, vulgar, socially unacceptable, if the team uses inappropriate form of communicating in the official channels, if the problems are discussed with people outside of the team during the competition or if an attack is attempted on the servers of the competition (guessing the passwords of other teams, intentional spam, unreasonable usage of server time, etc.)
  • In case of situation that could not be predicted or prevented by the organizers, the organizers reserve the right to declare their final decision on the matter as it comes and this decision will be made in accordance to the rules of fair play.
In case you are confused by some of the rules visit the FAQ section or contact us via email.