USAAAO 2021, I кръг — Задача 16
USAAAO 2021 - First Round · 30 януари 2021 г.
PHYSICAL AND ASTRONOMICAL CONSTANTS
| c | Speed of light in vacuum | |
| e | Elementary charge | |
| m | Neutron rest mass | |
| m | Proton rest mass | |
| m | Electron rest mass | |
| m | Helium-4 rest mass | |
| h | Planck’s constant | |
| H | Hubble’s constant | 70 (km/s)/Mpc |
| k | Boltzmann’s constant | |
| b | Wien’s constant | |
| G | Gravitational constant | |
| Stefan-Boltzmann constant | ||
| c | First Radiation Constant | |
| c | Second Radiation Constant | |
| N | Avogadro constant | |
| R | Gas constant | |
| a | Bohr radius | |
| Bohr magneton | ||
| M | Solar mass | |
| R | Solar radius | |
| L | Solar luminosity | |
| T | Solar temperature | 5770 K |
| M | Earth mass | |
| R | Mean Earth radius | |
| I | Earth moment of Inertia | |
| R☾ | Mean Moon radius | |
| M♃ | Mean Jupiter mass | |
| R♃ | Mean Jupiter radius | |
| a♃ | Mean orbital radius of Jupiter | 5.2 AU |
| a☾ | Mean semimajor axis Moon orbit | |
| 1 light year | ||
| 1 AU | Astronomical Unit | |
| 1 pc | Parsec | |
| 1 year | ||
| 1 sidereal day | 86164 s | |
| 1 erg | ||
| 1 bar |
ENERGY CONVERSION : 1 joule (J) = electronvolts (eV)
Условие
In a certain day, when it is 0h UT, the sidereal time of Prime Meridian is 5h 56min 9.4s. For this day, with start and end based on UT, find the civil time of Chicago, whose longitude and time zone are respectively, 87.65004722 W and UT-6, when the sidereal time there is 20h. The difference between solar time and sidereal time SHOULD be accounted for.
(a) 14h 1min 32s
(b) 13h 26min 17s
(c) 14h 36min 47s
(d) 14h 0min 43s
(e) 13h 51min 11s
Отговори
- E
Решение
We need to find the civil time of Chicago (UT-6) when the Sidereal Time of Chicago is 20h, for the day that begins when at 0h UT, the Sidereal Time of the Prime Meridian is 5h 56min 9.2s (5.9358889 sidereal hours).
The trick to solve this problem is to treat solar time and sidereal time with different units. Here, we will use sidereal hours and solar hours.
We know the difference between the sidereal times at any point in time:
Using this, we can find the sidereal time of the Prime Meridian when the Sidereal Time of Chicago is 20h.
Hence, we should add the Difference obtained to the Chicago Sidereal Time to obtain the Prime Meridian Sidereal Time when the former is 20h. For simplicity, we will label this instant as (2). We will label 0h UT as (1).
Hence, the time elapsed between (1) and (2) is:
Converting the Time Elapsed into solar hours:
We also know that:
Hence,
For Chicago, we have:
Answer: E
Оригинал в Архива: usaaao2021_exam1.pdf · официални решения: usaaao2021_exam1_solutions.pdf