© 2026 PhysElo. All rights reserved. Built by an IPhO · APhO · EuPhO representative.

TermsPrivacyRefundsReport Copyright / DMCA
PhysElo
HomeProblemsPOTWContestsRanksFeedback

The Ultimate Physics Arena

Work through 100+ olympiad-grade problems at your own pace, with AI hints when you're stuck and a discussion behind every problem.

Solve Problems →
Practice at your own pace
Problem of the Week →
Multi-part challenge problems
Problem of the DaySeptember 24, 2026

Keplerian Catch-Up

gravitationMedium
Two satellites move in the same circular orbit of radius rrr around a star, with speed vvv and period TTT, traveling in the same direction. Initially the second satellite is one quarter-orbit ahead of the first. The first satellite briefly fires its retrorockets, instantaneously reducing its speed and dropping into an…
Solve today's problem →

Top Solvers

  • 1
    dragon1mstThe 50 ClubSolved 50 or more problems in the problem bank
    58
  • 2
    RazziThe 50 ClubSolved 50 or more problems in the problem bank
    55
  • 3
    phoenix137
    Feb26' Champion
    Won 1st place in a monthly contest
    49
  • 4
    TarakeshwarMJ
    28
  • 5
    Tryingtoimprovemh
    14

134 students·846 answers submitted

Stuck? Get a nudge, not the answer.

When you're stuck, the droid gives you just enough to get moving again. Wrong answer? It points at where you slipped, not at the solution. And you can ask it questions, free, every day.

Try it on today's problem →

Problem Bank

Practice physics problems at your own pace. Filter by topic and difficulty, and track your progress as you go.

Problem of the Week (POTW)

Advanced, multi-part physics problems that take real work to crack. The strongest solvers earn exclusive badges.

Discussions

Every problem has its own discussion. Once you've solved it, compare your approach with everyone else who got there.