Astronomy (C894)

Correct Answer B. To travel in a spaceship and explore outer space

Explanation

The primary role of an astronaut is to travel into space to conduct experiments, explore outer space, and gather data. Astronauts may participate in missions that involve traveling to space stations, conducting spacewalks, and performing various scientific tasks related to space exploration.

Why other options are wrong

A. To conduct scientific research in laboratories

While astronauts do conduct scientific research, it is typically in space, not laboratories on Earth. Their work in space stations or spacecraft involves experiments in microgravity.

C. To design spacecraft and satellites

Astronauts are trained to operate and work within spacecraft and satellites, but designing these objects is the job of engineers and scientists, not astronauts.

D. To teach astronomy to students

Astronauts may share their experiences with students or engage in outreach activities, but teaching astronomy is not their primary role. Their focus is on space exploration and research

Correct Answer  C. Formed in the lives and deaths of giant ancestral stars

Explanation

Heavier elements, such as carbon, oxygen, and iron, were formed in the cores of giant stars through nuclear fusion. When these stars explode as supernovae, they scattered these elements throughout the universe, which eventually became part of the Earth and other celestial bodies.

Why other options are wrong

A. Formed in our sun

While the Sun does produce some heavier elements through fusion (such as helium), it does not have the necessary mass to create the heavier elements found on Earth. These elements were primarily formed in larger stars that went through supernova explosions.

B. Formed in the initial moments of the big bang

The Big Bang primarily produced the lightest elements, such as hydrogen, helium, and trace amounts of lithium and beryllium. Heavier elements formed later in stars, not during the Big Bang itself.

Correct Answer A. Backward

Explanation

When the spacecraft is slowing down, the astronaut inside will feel an apparent force pushing them backward. This is because of inertia; the astronaut's body wants to continue moving at the same speed as the spacecraft, but as the spacecraft decelerates, the astronaut experiences the sensation of being pushed backward relative to the spacecraft.

Why other options are wrong

B. Forward

A forward force would be felt if the spacecraft were accelerating, not slowing down. When slowing down, the apparent force is opposite to the direction of travel.

C. Sideways

There is no sideways force acting on the astronaut unless the spacecraft is turning, which is not mentioned in the scenario. The force is felt in the direction opposite to the deceleration (backward).

D. Vertically only

There is no mention of a vertical motion or force in the spacecraft. The apparent force is horizontal (backward) due to the spacecraft's deceleration.

E. Nowhere because there is no force

This statement is incorrect because the astronaut does experience a force due to the deceleration of the spacecraft. The force is felt as a backward push due to inertia.

Correct Answer C. It lies near the North Celestial Pole

Explanation

Polaris, also known as the North Star, lies very close to the North Celestial Pole, making it a crucial reference point for navigation in the Northern Hemisphere. Because of its position, it appears nearly stationary in the sky while other stars appear to rotate around it. This stability makes it useful for determining direction, especially for finding true north.

Why other options are wrong

A. It can sometimes be seen during the day

This is incorrect. While Polaris is a bright star, it is not visible during the day due to the brightness of the Sun. It can only be seen at night.

B. It displays retrograde motion

This is incorrect. Retrograde motion refers to the apparent motion of planets relative to the stars, not stars. Polaris does not exhibit retrograde motion.

D. It marks the vernal equinox

This is incorrect. The vernal equinox is marked by the Sun’s position as it crosses the celestial equator, not by a star. Polaris is located near the North Celestial Pole, but it is not related to the equinoxes.

E. Its position in the sky indicates the season

This is incorrect. While Polaris is a key star for navigation, its position in the sky does not directly indicate the season. Seasonal changes are marked by the position of the Sun and the Earth’s tilt, not by the position of Polaris.

Correct Answer A. Have greater masses

Explanation

The gravitational force between two objects is directly proportional to their masses, as described by Newton's law of gravitation. The larger the masses of the objects, the stronger the gravitational pull between them.

Why other options are wrong

B. Have rougher surfaces

The roughness of an object's surface does not affect the gravitational force between two objects. Gravitational force depends on mass and distance, not surface characteristics.

C. Are farther apart

Gravitational force weakens as the distance between two objects increases. The farther apart the objects, the weaker the gravitational pull between them.

D. Are moving at greater speed

The speed of the objects does not affect the gravitational force between them. The gravitational pull is determined by mass and distance, not motion speed.

Correct Answer F. A galaxy

Explanation

A galaxy is a vast collection of stars, gas, dust, and dark matter bound together by gravity, orbiting a common center. Our Milky Way is an example of such a galaxy, containing billions of stars that orbit the galactic center. The other options describe smaller celestial objects, such as moons, comets, and planets, none of which are large systems of stars like a galaxy.

Why other options are wrong

A. A moon

This is incorrect because a moon is a natural satellite that orbits a planet. It is much smaller than a galaxy and is not made up of a collection of stars.

B. A comet

This is incorrect because a comet is a small icy object that orbits the Sun. It does not consist of stars and is much smaller than a galaxy.

C. A planet

This is incorrect because a planet is a large body that orbits a star, not a collection of stars held together by gravity. A planet is much smaller than a galaxy.

D. A solar system

This is incorrect because a solar system consists of a star and the objects that orbit it, such as planets, moons, and asteroids. It does not consist of a collection of stars.

E. An asteroid

This is incorrect because an asteroid is a small rocky object that orbits the Sun, not a large collection of stars.

Correct Answer E. Rotation: 24 hours; revolution: 365.25 days

Explanation

Earth’s rotation period is 24 hours, which is the time it takes for Earth to complete one full spin on its axis, creating the day-night cycle. The revolution period, the time it takes for Earth to orbit the Sun, is about 365.25 days, which gives rise to a year. The extra 0.25 days are accounted for by leap years, which add an extra day every four years to keep our calendar year in sync with Earth's orbit.

Why other options are wrong

A. Rotation: 24 hours; revolution: 24 hours

This is incorrect because the revolution period of Earth around the Sun takes approximately 365.25 days, not 24 hours. The Earth’s revolution takes much longer than a single day.

B. Rotation: 24 hours; revolution: 365 days

While Earth's rotation does take 24 hours, its revolution actually takes 365.25 days, not exactly 365. This extra 0.25 days is accounted for by the leap year.

C. Rotation: 365 days; revolution: 24 hours

This is incorrect because the rotation period of Earth is 24 hours, not 365 days. Earth’s rotation is responsible for the daily cycle of day and night, and the revolution around the Sun takes 365.25 days.

D. Rotation: 24 hours; revolution: 27.3 days

This is incorrect because the revolution period of Earth around the Sun is not 27.3 days. This duration is close to the orbital period of the Moon around Earth, not Earth’s revolution around the Sun. Earth's revolution takes 365.25 days.

Correct Answer C. Kinetic energy, rest energy, and potential energy

Explanation

In a system consisting of a comet and a star, the system possesses multiple forms of energy. The comet has kinetic energy due to its motion, rest energy (from its mass according to Einstein’s famous equation, E=mc2E = mc^2), and potential energy due to the gravitational attraction between the comet and the star. All of these forms of energy are present as the comet moves through its elliptical orbit.

Why other options are wrong

A. Kinetic energy

While the system does have kinetic energy because the comet is moving, this option ignores the other forms of energy in the system, such as the gravitational potential energy between the comet and the star, and the rest energy of the objects.

B. Kinetic energy and rest energy

This option is partially correct, as the system does have kinetic energy and rest energy. However, it neglects the important gravitational potential energy between the comet and the star, which plays a significant role in the system's overall energy. Therefore, it is not a complete description of the system's energy.

Correct Answer A. astronomy

Explanation

Astronomy is the scientific study of celestial bodies such as stars, planets, comets, and galaxies, as well as the phenomena that originate outside Earth's atmosphere. It involves the observation and understanding of the universe beyond Earth.

Why other options are wrong

B. astrology

This is incorrect because astrology is a belief system that suggests that the positions and movements of celestial bodies influence human events. It is not a scientific discipline like astronomy.

C. earth sciences

This is incorrect because earth sciences involve the study of the Earth itself, including its structure, processes, and history. While astronomy may overlap in some areas (such as studying the Earth from space), earth sciences are distinct from astronomy.

D. physics

This is incorrect because physics is the study of the fundamental principles of matter and energy in the universe. While physics is essential to understanding the mechanics of astronomy, it is a broader field that includes many other areas, not just celestial phenomena.