First Astronomy Exam Smart Work Answers
Which of the following values given for the Doppler shifts of astronomical bodies indicates that the object is approaching fastest (blue shifted)?
-0.06 nm
If the distance between Earth and the Sun were cut in half, the gravitational force between these two objects would
increase by a factor of 4.
If we wanted to increase the Hubble Space Telescope's altitude above Earth and keep it in a stable orbit, we also would need to
increase its orbital speed.
Suppose you are transported to a planet with twice the mass of Earth, but the same radius of Earth. Your weight would __________ by a factor of __________.
increase; 2
If you went to Mars, your weight would be
lower because Mars has lower mass and a smaller radius that together produce a lower gravitational force.
1.60934 x 103 (the number of meters in a mile): 9.154 x 10-3 (Earth's diameter compared to the Sun's):
1609.34 0.009154
What is the minimum amount of time it would take a photon of light from Jupiter to reach Earth?
34.9 minutes
What is the greatest distance (in degrees) that a star can be from Polaris and still be circumpolar as seen from Anchorage AK (latitude 60.0 °)?
60.0
Suppose we find an Earth-like planet around one of our nearest stellar neighbors, Alpha Centauri (located only 4.4 light-years away). If we launched a "generation ship" at a constant speed of 1750.00 km/s from Earth with a group of people whose descendants will explore and colonize this planet, how many years before the generation ship reached Alpha Centauri? (Note there are 9.46 ××1012 km in a light-year and 31.6 million seconds in a year.)
7.53 X 10^2 years
If an event were to take place on the Sun, how long would it take for the light it generates to reach us?
8 Minutes
Convert the number 86496.0000 into scientific notation where the scientific notation is defined as 𝑋×10^4. Enter the correct value for X.
8.6496
How does the spectrum of a distant star reveal the star's chemical composition?
Dark lines, also called absorption lines, within the spectra are "fingerprints" for the different atoms and molecules within a star's atmosphere.
A light-year is a measure of
Distance
If the Sun instantaneously stopped giving off light, what would happen on Earth?
Earth would get dark 8 minutes later.
Why is there an angle between the ecliptic and the celestial equator?
Earth's axis is tilted with respect to its orbit.
The scientific method is a way of trying to ______________ ideas; thus all scientific knowledge is provisional.
Falsify, not prove,
Rank the following in order of size, from smallest to largest.
1. The radius of Earth 2. A little-minute 3. The distance from Earth to the Sun 4. A light-hour 5. The radius of the Solar System 6. A light-year
Place the following phases of the Moon in order, starting with a full Moon.
1. full moon 2. waning gibbous 3. waning crescent 4. new moon 5. waxing crescent 6. waxing gibbous
A net force must be acting when an object (select all that apply):
A.accelerates. B.changes speed but not direction. C.changes direction but not speed. D.changes speed and direction.
Where on Earth can you stand and, over the entire year, see the entire sky?
At the equator
The tilt of Earth's axis causes the seasons because
B. the days are longer in summer. C. the rays of light strike the ground more directly in summer.
Following the invention of the telescope, astronomers were able to measure the speed of light by observing Jupiter's moons passing behind Jupiter in their orbit and becoming eclipsed. Study the figure, which shows how someone on Earth can view Jupiter's moon's eclipses when Earth is closer to or farther from Jupiter, and determine which of the following are correct.
B.If light has infinite speed, an eclipse would be seen to happen at the same time regardless of how far away Earth is from Jupiter. C.If light has finite speed, it would take longer for it to travel from Jupiter to Earth when Earth is farther from Jupiter.
Which stars we see at night depends on A.the motion of stars relative to one another over the course of the year. B.the time of the observation. C.our location on Earth. D.Earth's location in its orbit.
B.the time of the observation. C.our location on Earth. D.Earth's location in its orbit.
Occam's razor states that
If two hypotheses fit the facts equally well, choose the simpler one.
Suppose you read on the Web that a new planet has been found. Its average speed in its orbit is 33 kilometers per second (km/s). When it is closest to its star, it moves at 31 km/s, and when it is farthest from its star, it moves at 35 km/s. This story is in error because
Kepler's second law says the planet must move fastest when it is closest, not when it is farthest away.
A planet moves fastest when it is _______ to the Sun and slowest when it ________ is from the Sun.
Nearest, Farthest
For Earth, P^2/A^3 = 1.0 (in appropriate units). Suppose a new dwarf planet is discovered that is 14 times as far from the Sun as Earth is. For this planet
P^2/A^3 = 1.0.
Day and night are caused by the
Rotation of the earth on its axis
Newton determined that the force of gravity on an object is proportional to its mass, causing its mass to be canceled out (Newton's second law) and resulting in a constant acceleration. If the laws of physics are universal, then Newton should be able to apply his discoveries about gravity on Earth to the motion of the planets in our Solar System. Newton's third law says that for every force there is an equal reaction force in the opposite direction. What does this imply about the force of gravity associated with a person standing on the Earth?
The Earth's gravity pulls downward on the person, and the person's gravity pulls upward on the Earth.
Newton's second law says that the acceleration (a) of an object depends on its mass (m) by the equation: a=f/m F is the force that is causing the object to accelerate. In the case of dropping objects from a height, the force that causes them to accelerate toward the Earth is gravity. If the acceleration of objects dropped from a height does not depend on the object's mass (as shown by Galileo's experiment), what does this imply about the force of gravity?
The force of gravity increases with increased mass.
Newton developed a universal law of gravitation that can be used under most circumstances, not just for objects on the surface of the Earth. Here is the law:𝐹=𝐺 𝑚1𝑚2/𝑟2 where G is a constant.Think about what happens when you increase and decrease each of the variables in Newton's equation for the gravitational force between two objects of mass m1 and m2, a distance r from one another.
The force of gravity is stronger closer to the Sun.
Astronauts in a space shuttle can float while orbiting Earth. Why are these astronauts weightless?
They are falling around Earth at the same rate as the shuttle.
Imagine a planet moving in a perfectly circular orbit around the Sun. Is this planet experiencing acceleration?
Yes, because it is changing its direction of motion all the time
The average distance of Mars from the Sun is 1.4 AU. How bright is the Sun on Mars compared with its brightness on Earth?
about 2 times fainter
How would you describe the shape of Mercury's orbit?
as an ellipse
If you were standing at Earth's North Pole, where would you see the north celestial pole relative to your zenith?
at the zenith
When you look at the sky on a dark night and see stars of different colors, which are the hottest?
blue
Light acts like
both a wave and a particle.
No matter where you are on Earth, stars appear to rotate about a point called the
celestial pole
As wavelength increases, the energy of a photon __________ and its frequency __________.
decreases; decreases
When Earth catches up to a slower-moving outer planet and passes it in its orbit, in the same way that a faster runner overtakes a slower runner in an outside lane, the outer planet
exhibits retrograde motion.
The scientific method is a process by which scientists
gain confidence in theories by failing to prove them wrong.
Weight refers to the force of gravity acting on a mass. We often calculate the weight of an object by multiplying its mass by the local acceleration due to gravity. The value of gravitational acceleration on the surface of Mars is 0.377 times that on Earth. If your mass is 85 kg, your weight on Earth is 830 N (m × g = 85 kg × 9.8 m/s2 = 830 N). What would be your approximate mass and weight on Mars?
mass 85 kg; weight 310 N
As a blackbody becomes hotter, it also becomes __________ and __________.
more luminous; bluer
When you turn on a lightbulb in a room, the entire room appears to flood with light at the same time. Your eyes cannot perceive light originating at the bulb and then moving outward from it. This either means that light has infinite speed (appears everywhere instantaneously), or it moves so fast that it is difficult to tell the difference. How might you improve your chances of detecting the motion of light if it moves at finite speed?
move farther away from the light source
The cosmological principle states that
on a large scale, the universe is the same everywhere at a given time.
Kepler's second law says that
planets move fastest when they are closest to the Sun.
Newton's second law of motion states that
the acceleration of an object is proportional to the net force acting on it.
Compared to your mass on Earth, on the Moon your mass would be
the same; mass doesn't change.
