Astronomy Homework Questions

Which object has more gravitational potential energy? A 100-kilogram satellite orbiting Jupiter or a 100-kilogram satellite orbiting Earth. (Assume both satellites orbit at the same distance from their planets' center.)

100-kg satellite orbiting Jupiter

Compare the diameter of Betelgeuse, 1.38x10^9, to the average Earth-Sun distance, 149.6 million km.

9.2

The diameter of the giant star Betelgeuse is 1.38x10^9 km. How does this compare to the diameter of the Sun, whose diameter is 1.39 million km.

993

Earth's radius is approximately 6370 km. What is its circumference?

C=4.00x10^4 km

Earth is closer to the Sun in January than in July. Therefore, in accord with Kepler's second law: a) Earth travels faster in its orbit around the Sun in January than in July. b) It is summer in January and winter in July. c) Earth travels faster in its orbit around the Sun in July than in January.

Earth travels faster in its orbit around the Sun in January than in July.

List the different forms of light in order from highest to lowest energy.

Gamma, x-rays, UV, visible light, infrared, radio

True or false: This morning I saw the full moon setting at about the same time the Sun was rising.

True

Which object has more gravitational potential energy? A bowling ball perched on a cliff ledge or a baseball perched on the same ledge.

bowling ball

Find the orbital period: A planet with twice Earth's mass orbiting at a distance of 1 AU from a star with the same mass as the Sun.

1 year

Suppose that all the mass in your body were suddenly converted into energy according to the formula E=mc^2, and 6.3x10^18 J of energy were released. Compare this to the energy released by a 1 megaton hydrogen bomb (5x10^15 J).

1260

What distance is represented by each arcminute of latitude?

40003.6/360/60=1.85 km

Which of the cars is accelerating? a) A car traveling on a straight, flat road at 50 miles per hour. b) A car going around a circular track at a steady 100 miles per hour. c) A car traveling on a straight uphill road at 30 miles per hour.

A car going around a circular track at a steady 100 miles per hour.

A satellite in geostationary orbit appears to remain stationary in the sky as seen from any particular location on Earth. Why does a geostationary satellite must orbit Earth in 1 sidereal day, rather than 1 solar day? a) A satellite rotating at a period of one solar day would not be seen from Earth, because it will be outshined by the Sun. b) Actual period of the Earth's rotation is sidereal day. Solar day is a bit longer because of the Earth's orbital motion. c) A geostationary satellite should rise and set at the same time each day, and Sun sets and rises at different time during the year. d) Earth's sidereal day and Earth's solar day are the same time interval, so there is no difference actually.

Actual period of the Earth's rotation is sidereal day. Solar day is a bit longer because of the Earth's orbital motion.

True or false: Because of precession, someday it will be summer everywhere on Earth at the same time.

False

Compared to their values on Earth, on another planet a) your weight would be the same but your mass would be different. b) your mass and weight would both be the same. c) your mass would be the same but your weight would be different.

your mass would be the same but your weight would be different.

You are an astronomer on planet Nearth, which orbits a distant star. It has recently been accepted that Nearth is spherical in shape, though no one knows its size. One day, while studying in the library of Alectown, you learn that on the equinox your sun is directly overhead in the city of Nyene, located 1400 kilometers due north of you. On the equinox, you go outside and observe that the altitude of your sun is 78 degrees. What is the circumference of Nearth?

1400(360/12)=4.2x10^4 km

What distance is represented by each degree of latitude on Earth if Earth's diameter is 40003.6 km?

40003.6/360=111 km

Suppose that all the mass in your body were suddenly converted into energy according to the formula E=mc^2. How much energy would be released? (Assume that your mass is about 70 kilograms).

6.3x10^18 J

In winter, Earth's axis points toward the star Polaris. In spring, the axis points toward: a) Polaris b) Vega c) Sun

Polaris

Choose the correct definition and two examples of potential energy. a) Potential energy is energy of close molecules' interaction. Two examples are thermal energy of molecules of hot air and mechanical energy of a rock on the top of a hill. b) Potential energy is energy of close molecules' interaction. Two examples are chemical energy in a breakfast cereal and mechanical energy in a compressed spring. c) Potential energy is energy that is stored. Two examples are mechanical energy of a car driving down the highway and thermal energy of molecules of hot air. d) Potential energy is energy that is stored. Two examples are mechanical energy in a compressed spring and gravitational energy in a rock on the top of a hill.

Potential energy is energy that is stored. Two examples are mechanical energy in a compressed spring and gravitational energy in a rock on the top of a hill.

Choose the correct definition of precession, and the correct explanation how does it affect what we see in our sky. a) Precession is the change of direction in which Earth's axis points. The celestial poles slowly move relative to the stars. In about 13000 years the star Vega will be the North star instead of Polaris. b) Precession is the angle at which Earth's axis tilted from the perpendicular to the ecliptic plane. Because of that angle, seasons occur during the year. When Northern Hemisphere is tilted to the Sun, there are summer in Northern and winter in Southern Hemispheres. c) Precession is irregularity in Earth's rotation during the year. The duration of day and night changes during the year because the precession. The longest day is at summer solstice, June 21, and the shortest day is at winter solstice, December, 21. d) Precession is the change of Earth's rotation rate. The duration of sederael day slowly increases over the centuries. In about 50000 years the duration of the siderial day would be about 1 minute longer than today.

Precession is the change of direction in which Earth's axis points. The celestial poles slowly move relative to the stars. In about 13000 years the star Vega will be the North star instead of Polaris.

Choose the correct definition and two examples of radiative energy. a) Radiative energy is energy in the form of light. Sunlight and radio waves carry this form of energy. b) Radiative energy represent energy of many individual particles. Sunlight and molecules of liquid in a cup of hot coffee carry this form of energy. c) Radiative energy represent energy of many individual particles. Sunlight and molecules of hot, raising up air carry this form of energy. d) Radiative energy is energy in the form of light. Sunlight and acoustic waves carry this form of energy.

Radiative energy is energy in the form of light. Sunlight and radio waves carry this form of energy.

Which person is weightless? a) A child in the air as she plays on a trampoline. b) A scuba diver exploring a deep-sea wreck. c) An astronaut on the Moon.

A child in the air as she plays on a trampoline.

Estimate the diameter of the supergiant star Betelgeuse, using its angular diameter of about 0.05 arcsecond and distance of about 600 light-years.

D=1.38x10^9 km

True or false: If Earth's orbit were a perfect circle, we would not have seasons.

False

True or false: There's no gravity in space.

False

Which object has more gravitational potential energy? A diver on a 10-meter platform or a diver on a 3-meter diving board.

diver on 10-meter platform

As an interstellar gas cloud shrinks in size, its gravitational potential energy: a) stays the same at all times. b) gradually transforms into other forms of energy. c) gradually grows larger.

gradually transforms into other forms of energy.

If there is going to be a total lunar eclipse tonight, then you know that: a) the Moon's phase is full. b) the Moon's phase is new. c) the Moon is unusually close to Earth.

the Moon's phase is full

Is Polaris a circumpolar star in New York's sky?

Yes

The north celestial pole is 30 degrees above your northern horizon. What does it tell you? a) You are at longitude 30 degrees W. b) You are at latitude 30 degrees N. c) You are at latitude 30 degrees S.

You are at latitude 30 degrees N.

Suppose you experience 6 gees of acceleration in a rocket. What is your acceleration in meters per second squared?

58.8 m/s^2

Suppose you experience 6 gees of acceleration in a rocket. You will feel a compression force from the acceleration. How does this force compare to your normal weight?

6

Find the orbital period: A planet with the same mass as Earth orbiting at a distance of 1 AU from a star with four times the Sun's mass.

6 months

The dwarf planet Eris orbits the Sun every 557 years. What its average distance (semi major axis) from the Sun?

67.7 a.u.

Choose the correct definition and two examples of kinetic energy. a) Kinetic energy is the energy an object has due to its motion. A car driving down the highway or molecules of hot, raising up air have kinetic energy. b) Kinetic energy is the energy an object has due to its position. A car driving down the highway or molecules of hot, raising up air have kinetic energy. c) Kinetic energy is the energy an object has due to its motion. A car resting on the top of a hill or molecules of hot, raising up air have kinetic energy. d) Kinetic energy is the energy an object has due to its position. A car resting on the top of a hill or molecules of hot, raising up air have kinetic energy.

Kinetic energy is the energy an object has due to its motion. A car driving down the highway or molecules of hot, raising up air have kinetic energy.

Suppose Earth had a second moon, called Swisscheese, with an average orbital distance double the Moon's and a mass about the same as the Moon's. Is Swisscheese's orbital period longer or shorter than the Moon's?

Longer

The Sun's diameter is 1,390,000 km, and its distance from Earth ranges between 147.5 and 152.6 million km. Find the Sun's angular size at its minimum and maximum distances from Earth.

Min.: 0.5399 degrees Max.: 0.5219

The Moon's precise equatorial diameter is 3,476 km, and its orbital distance from Earth varies between 356,400 km and 406,700 km. Find the Moon's angular size at its maximum and minimum distances from Earth.

Min.: 0.5588 degrees Max.: 0.4897 degrees

New York City has coordinates of 40 degrees N and 74 degrees W. Where does the north or south celestial pole appear in the sky of New York?

The north celestial pole appears in the sky of New York at an altitude of 40 degrees north.

Beijing and Philadelphia have about the same latitude but different longitudes. What can be said about the tonight's night sky in these two places? a) The sky will look about the same. b) The sky will have completely different sets of constellations. c) The sky will have partially different sets of constellations.

The sky will look about the same.

"Although all the known stars rise in the east and set in the west, we might someday discover a star that will rise in the west and set in the east." Choose the correct explanation why does the statement above make sense (or is clearly true) or does not make sense (or is clearly false). a) This statement does not make sense. The stars moves because of the Galaxy's rotation around it center. So, during the day, al the stars must move in the same direction. b) This statement makes sense. The North Star itself does not appear to move usually, but sometimes the precession occurs. Precession changes the tilt of Earth's axis and could make the North star set in east or rise in west. c) This statement does not make sense. The stars appear to rise and set because of Earth's rotation. So, during the day, all the stars must move in the same direction. d) This statement makes sense. The star appear to rise and set because of the sum of Earth's rotation and changing the seasons. So, in the night of solstice, the North Star could move in the opposite direction to other stars.

This statement does not make sense. The stars moves because of the Galaxy's rotation around it center. So, during the day, al the stars must move in the same direction.

If an astronaut goes on a space walk outside the Space Station, she will quickly float away from the station unless she has a tether holding her to the station. Choose the correct explanation why does the statement make sense (or is clearly true) or does not make sense (or is clearly false). a) This statement is true. She and the Space Station cannot share the same orbit and will move apart quickly. b) This statement is false. She and the Space Station have different orbits at the beginning but will stay together due to mutual gravity. c) This statement is false. She and the Space Station share the same orbit and will stay together unless they are pushed apart. d) This statement is true. She and the Space Station have different orbits at the beginning and will move apart.

This statement is false. She and the Space Station share the same orbit and will stay together unless they are pushed apart.

True of false: If an astronaut goes on a space walk outside the Space Station, she will quickly float away from the station unless she has a tether holding her to the station. a) This statement is true. She and the Space Station cannot share the same orbit and will move apart quickly. b) This statement is false. She and the Space Station have different orbits at the beginning but will stay together due to mutual gravity. c) This statement is false. She and the Space Station share the same orbit and will stay together unless they are pushed apart. d) This statement is true. She and the Space Station have different orbits at the beginning and will move apart.

This statement is false. She and the Space Station share the same orbit and will stay together unless they are pushed apart.

"I live in the United States, and during my first trip to Argentina I saw many constellations that I'd never seen before." Choose the correct explanation why the statement makes sense (or is clearly true) or does not make sense (or is clearly false). a) This statement makes sense, because the constellations visible in the sky depend on latitude. Since Argentina is in the Southern Hemisphere, the constellations visible there include many that are not visible from the United States. b) This statement makes sense, because the constellations visible in the sky depend on longitude. Since Argentina is to the East from the US, the constellations visible there include many that are not visible from the United States. c) This statement doesn's make sense, because the constellations visible in the sky depend on longitude. Since Argentina is at the the same longitude, as the US are, the constellations visible there are mostly visible from the United States. d) This statement doesn's make sense, because the constellations visible in the sky depend on latitude. Since Argentina is in the Northern Hemisphere, the constellations visible there are mostly visible from the United States.

This statement makes sense, because the constellations visible in the sky depend on latitude. Since Argentina is in the Southern Hemisphere, the constellations visible there include many that are not visible from the United States.