PC2023-P3 Best solutions and final results

Problem 3 – Magnets in conducting liquid

In total, 62 solutions were submitted for problem 3, out of which 18 were correct.
Congratulations to everyone who managed to solve this problem!

The Best Solution Awards are usually selected from those solutions which were submitted before any hints, sometimes with the exception of Hint 1 which is usually very subtle. This time, however, the first correct solution was submitted after the second hint. Because of that, half of the best-solution award goes to the single participant who solved the problem with two hints, Luka Passek-Kumerički. The remaining half is distributed evenly, between the only two contestants who solved the problem with three hints, Anindya Guria and Chung Wang Lam; both of them earn one-quarter of the award. All these solutions are clear and well-written.

When seeing that the problem turned out to be more difficult than expected, with no correct solutions for a long time, I asked a few former Physics Cup winners to try out this problem. As a result, we have also two excellent solutions, written by Dobrica Jovanovic, currently a second-year undergraduate student at MIT, and Thomas Foster, currently a graduate student at Princeton University. These are both really excellent solutions. The solution by Thomas Foster in particular provides additional insight into the problem and useful discussions.

Final results for Problem 3

Pre-university students:

First nameSurnameCountrySchool/UniversityP3 timeP3 Score
Chung WangLamHong KongSt. Paul’s Co-educational College25/2/23 15:522.0982
AlexandarRoussevBulgaria27/2/23 10:021.4148
Ilan, Ivan (Team)Mihelja, HegedićCroatiaXV. gymnasium Zagreb, V. gymnasium Zagreb27/2/23 11:051.2862
EppuLeinonenFinlandMunkkiniemen yhteiskoulu6/3/23 18:270.8858
FilipVučićCroatiaI. gymnasium Zagreb1/3/23 17:300.8524
TomasBabelisLithuaniaVilniaus jėzuitų gimnazija20/3/23 12:520.6588
RuichengMaChinaHarbin Normal University High School19/3/23 22:380.6523
DženanMidžićBosnia and HerzegovinaJU Gimnazija “Bihać”1/4/23 11:460.599

University students:

First nameSurnameCountrySchool/UniversityP3 timeP3 Score
LukaPassek-KumeričkiCroatiaUniversity of Zagreb17/2/23 20:323.079
AnindyaGuriaIndiaIndian Institute of Science26/2/23 13:381.9074
KerimCherkezovTurkmenistanTurkmen State University28/2/23 04:471.2862
LukasSchichtGermanyUniversity of Rostock4/3/23 18:291.1108
AlessioBiccariItalyLa Sapienza11/3/23 21:230.7972
GilRonenIsraelHebrew University of Jerusalem12/3/23 09:040.7247
TejasAcharyaIndiaUniversity of Oxford28/3/23 20:330.605
SoumyadeepSarmaIndiaIndian Institute of Science26/3/23 06:190.599
KonstantinTripunovskiNorth MacedoniaUniversity of Ljubljana – Medical Faculty21/3/23 15:330.593
MarinusLehmannGermanyUniversity of Potsdam30/3/23 10:560.495

The list of countries:
Algeria, Argentina, Armenia, Australia, Austria, Azerbaijan, Bahrain, Bangladesh, Belarus, Belgium, Bosnia and Herzegovina, Brazil, Bulgaria, Cambodia, Cameroon, Canada, China, Croatia, Cuba, Czech Republic, Ecuador, Egypt, El Salvador, Estonia, Finland, France, Georgia, Germany, Greece, Guatemala, Honduras, Hong Kong, Hungary, India, Indonesia, Iran, Israel, Italy, Japan, Kazakhstan, Kenya, Kosovo, Kyrgyzstan, Latvia, Lithuania, Macau, Malaysia, Mexico, Moldova, Montenegro, Nepal, Netherlands, Nigeria, North Korea, North Macedonia, Pakistan, Peru, Philippines, Poland, Romania, Russia, Rwanda, Saudi Arabia, Serbia, Singapore, Slovakia, Slovenia, South Africa, South Korea, Spain, Sri Lanka, Suriname, Sweden, Switzerland, Syria, Taiwan, Tajikistan, Thailand, Turkey, Turkmenistan, Ukraine, United Arab Emirates, United Kingdom, United States, Uzbekistan, Vietnam.