Brief rules

  • Online Physics Brawl is a three-hour long team competition happening over the Internet.
  • 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

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

Basic information

  • Teams consist of 1–5 players.
  • Every team is a member of one of the following two categories:
    • high school students – every team member must be enrolled in a high school (or in a middle school/elementary school), and no member can be older than 20 years
    • open – everyone who cannot or does not want to be in the first category.
  • 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 40 problems in the competition (excluding the hurry up part — see later). 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
    • 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 consists of three parts (the times are in the UTC+1 time zone):
    • First part: 17:00 to 18:30.
    • Second part: 18:30 to 20:00.
    • Hurry-up part: 18:00 to 18:30.
  • The competition will end at 20:00 (3 hours after it began).
  • In the first part, each team will be given the first 7 problems. Once a team solves a problem, it will gain access to the next problem.
  • Teams are awarded points for answering problems correctly. Every problem specifies a maximum amount of points a team can get by solving it. You can submit an answer to a problem as many times as you wish. However, you get the maximum amount of points only if you answer correctly the first time. 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.
  • If you answer incorrectly, your team will not be able to submit any answers in that particular group for 1 minute.
  • Second part is essentially the same as the first part apart from the fact teams will have the opportunity not to answer a given problem and to get an access to another problem instead. This action will be penalized by one point. You can skip problems only if you have more than -7 points.
  • If two teams happen to end up with the same number of points, the team who solved their last problem earlier will be considered better and if it is still a tie then the higher average point gain per problem will decide.


  • An hour after the beginning of the competition, teams will be enabled to answer the problems in the so-called Hurry-up series.
  • Teams can submit answers to these problems only during a period of 30 minutes. In this time, you are free to submit answers to the problems from the first part as well.
  • The problems are divided into three groups according to their topic. When the Hurry-up series is activated, teams are given one problem from each of these groups. Correctly answering a problem will grant you access to the next problem in the same group.
  • 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, you will be given a bonus. This bonus is equal to the number of points you received for solving this triplet of problems.
  • If you answer a problem from the Hurry-up series incorrectly, the possible amount of points you can get for this particular problem decreases by one. Therefore, unlike the problems in the first/second part, you can get zero points for a problem in the Hurry-up series.

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!

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.