USAAAO 2024, I кръг — Задача 20
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
Imagine a very long cylindrical planet that has a satellite orbiting around it. Considering that the average density of the planet is and the radius is , find the expression that relates the period of the satellite with its distance to the center of the planet.
(a)
(b)
(c)
(d)
(e)
Отговори
- B
Решение
Solution:
Due to the symmetry, and using Gauss’ Law for gravitation, we know that the gravity at a distance from the center is given by . Our Gaussian shape will thus be a cylinder of radius and length . So, , and the internal mass is given by . Therefore, we have that:
Now, knowing that , we can find the period:
Answer: B
Оригинал в Архива: usaaao_first_exam_2024-3.pdf · официални решения: usaaao_first_exam_2024_solutions-1.pdf