天體物理：練習題

A satellite is in a circular orbit around a planet. The radius of the orbit is \( 2.5 \times 10^{7} \text{ m} \) and the orbital period is \( 5.0 \times 10^{4} \text{ s} \). What is the orbital speed of the satellite?

Which of the following correctly describes the possible evolutionary stages of a star with a mass significantly larger than the mass of the Sun after it leaves the main sequence?

An object weighs \( 100 \text{ N} \) on Earth, where the gravitational field strength is \( 10 \text{ N/kg} \). What would the object weigh on a planet that has twice the mass of Earth and twice the radius of Earth?

Which of the following correctly lists the classification of stars by their surface temperature color, ordered from the coolest surface temperature to the hottest?

Contrast the final stages of the life cycle of a star with a mass similar to the Sun to that of a star with a mass much larger than the Sun.

A moon travels in a circular orbit around a planet at a radius of \(1.8 \times 10^{8}\) m. If the orbital period is \(3.0 \times 10^{6}\) s, calculate its orbital speed in m/s.

A communication satellite is in a circular orbit around the Earth at an altitude where the orbital radius is \(42,000\text{ km}\). The satellite takes \(24\text{ hours}\) to complete one full orbit.

(a) Calculate the orbital speed of the satellite in \(m/s\). Show your working and use \(\pi = 3.14\).
(b) Explain why the satellite is accelerating even if its orbital speed remains constant.