USAAAO 2024, I кръг — Задача 13
USAAAO 2024 - First Round · 10 февруари 2024 г.
Problem writers
Wesley Andrade, Abhay Bestrapalli, Austin Chen, Justin Chen, Ved Gund, Hagan Hensley, Sandesh Kalantre, Evan Kim, David Lee, Joe McCarty, Arjun Patel, Sahil Pontula, Tara Rezaei, Raul Teixeira, Leo Yao, David Zhang
Условие
Samvit observes a binary star system of masses and . Unfortunately, the star with mass is too dim for him to observe it, leading to the following snapshot below.

What could Samvit hypothesize to be the position and mass of the other star at this instant that would be consistent with the laws of physics and the orbit snapshot that he sees? To be clear, he has no knowledge of the value of or the period of the binary system.
(a) At with mass
(b) At with mass
(c) At with mass
(d) At with mass
(e) At with mass
Отговори
- D
Решение
Solution: The trick to this question is that the center of mass of the system has to lie at the focus of the ellipse, and this is the only thing that matters if you have no knowledge of the other parameters in the system. In fact, if you had the period of the binary system, you could fully determine the value of in terms of and the other parameters of the problem. So, we can simply go through the choices and see which choice places the center of mass of the system at one of the foci, , and choice (d) does.
Answer: D
Оригинал в Архива: usaaao_first_exam_2024-3.pdf · официални решения: usaaao_first_exam_2024_solutions-1.pdf