ASTR 263 HW Review (4, 5, 7-10, and 24)
Suppose two objects are attracting each other gravitationally. If you double the distance between them, the strength of their gravitational attraction __________.
decreases by a factor of 4
According to the universal law of gravitation, if you triple the distance between two objects, then the gravitational force between them _________.
decreases by a factor of 9
In the formula E = mc2, what does E represent?
the mass-energy, or potential energy stored in an object's mass
If you are driving at 30 miles per hour and increase your speed to 60 miles per hour, you quadruple your kinetic energy. True or False?
True.
If you double the mass of fusion material in a hydrogen bomb, you quadruple the amount of energy generated. True or False?
False.
As you watch the video, notice that the size of the tidal bulges varies with the Moon's phase, which depends on its orbital position relative to the Sun. Which of the following statement(s) accurately describe(s) this variation?
-Low tides are lowest at both full moon and new moon. -High tides are highest at both full moon and new moon.
Provided following are stages that occurred during the formation of our solar system. Rank these stages from left to right based on when they occurred, from first to last.
-large cloud of gas and dust -contraction of solar nebula -condensation of solid particles -accretion of planetesimals -clearing the solar nebula *Once the solar wind helped clear away the remaining gas in the solar nebula, the era of planet formation was essentially over. Remember that all these stages occurred over a period of millions of years, ending about 4 1/2 billion years ago.
Characteristics of TERRESTRIAL PLANETS:
-located within the inner solar system -solid, rocky surface -small size
What are the forms of electromagnetic radiation?
-microwaves -visible light -infrared -ultraviolet -gamma rays -X rays -radio waves *As explained in your textbook and the video, light is an electromagnetic wave that travels at the speed of light. Therefore all the regions of the electromagnetic spectrum can be thought of as different forms of light.
Characteristics of JOVIAN PLANETS:
-numerous orbiting moons -large planets but with low average density -extensive ring systems -primarily composed of hydrogen, hydrogen compounds, and helium
List the different forms of light in order from highest to lowest energy.
-radio -infared -visible -ultraviolet -XRays -Gamma Rays *We would get the same order if we listed forms of light by frequency (lowest to highest, left to right), since energy is directly proportional to frequency. It is the opposite of what we get if we list them by wavelength (shortest to longest, left to right), because frequency and wavelength are inversely related.
Of the temperature ranges below, which range represents the smallest range of actual temperature? -50-100° Celsius -50-100° Fahrenheit -50-100° Kelvin -They all represent the same change in temperature.
50-100° Fahrenheit
Suppose that the Sun were to collapse from its current radius of about 700,000 km to a radius of only about 6000 km (about the radius of Earth). What would you expect to happen as a result?
A tremendous amount of gravitational potential energy would be converted into other forms of energy, and the Sun would spin much more rapidly.
As discussed in the Extraordinary Claims box, when the giant impact idea was first proposed, it was generally thought to be so unlikely that it wasn't seriously considered until decades alter, after the Apollo missions to the Moon. What key piece of scientific understanding was missing that made it seem so unlikely when first proposed?
An understanding of the number and size of leftover planetesimals in the early solar system.
As the cloud shrinks in size, its central temperature increases as a result of its gravitational potential energy being converted to thermal energy.
As the cloud shrinks in size, its gravitational potential energy decreases. Because energy cannot simply disappear, the "lost" gravitational potential energy must be converted into some other form. Some of it is converted into thermal energy, which raises the temperature of the gas cloud. The rest is mostly converted into radiative energy, which is released into space as light.
Consider the three items from Part A that are not relevant to the giant impact hypothesis. As you'll learn in later chapters, the lack of volcanoes is a result of the Moon's relatively small size. But what explains the other two items — the Moon's synchronous rotation and gradually increasing distance from Earth?
Both are results of tidal interactions between the Moon and Earth. *As discussed in the section of your textbook on tides, the Moon's synchronous rotation arose as tidal friction slowed the Moon's rotation until its period matched its orbital period. The Moon's gradually increasing distance is a result of the fact that tidal friction is still gradually slowing Earth's rotation, and this leads to forces that push the Moon outward in its orbit so that the total angular momentum of the Earth-Moon system remains conserved.
The nebular theory also predicts that the cloud will flatten into a disk as it shrinks in size. Which of the following best explains why the collapsing cloud should form a disk?
Colliding cloud particles exchange angular momentum and, on average, end up with the rotation pattern for the cloud as a whole. *Particles in the collapsing cloud inevitably collide with one another. These collisions allow particles to exchange angular momentum, but their total angular momentum must be conserved. Therefore, many collisions result in an averaging out of the angular momentums of individual cloud particles, a process that brings their orbits into approximately the same plane.
Choose the correct definition of electrical charge.
Electrical charge is a measure of how strongly something will interact with electromagnetic fields.
The solar system has two types of planets, terrestrial and jovian. According to the nebular theory, why did terrestrial planets form in the inner solar system and jovian planets in the outer solar system?
Ices condensed only in the outer solar system, where some icy planetesimals grew large enough to attract gas from the nebula, while only metal and rock condensed in the inner solar system, making terrestrial planets. *Only metal and rock could condense at the high temperature of the inner solar system, so the inner planets were built by the accretion of metal and rock. Farther out, ices could also condense, leading to the accretion of ice-rich planetesimals. Some of these grew large enough for their gravity to attract gas from the solar nebula and become jovian planets.
Why are the inner planets made of denser materials than the outer planets?
In the inner part of the nebula only metals and rocks were able to condense because of the high temperatures, whereas hydrogen compounds, although more abundant, were only able to condense in the cooler outer regions.
Why is Newton's version of Kepler's third law so useful to astronomers?
It can be used to determine the masses of many distant objects.
Why did the solar nebula flatten into a disk?
It flattened as a natural consequence of collisions between particles in the spinning nebula, changing random motions into more orderly ones.
Suppose that two asteroids are orbiting the Sun on nearly identical orbits, and they happen to pass close enough to each other to have their orbits altered by this gravitational encounter. If one of the asteroids ends up moving to an orbit that is closer to the Sun, what happens to the other asteroid?
It will end up on an orbit that is farther from the Sun. *Total energy must be conserved, so if one asteroid loses energy and moves to a closer orbit, the other must gain energy and move to a more distant orbit.
What is the Oort cloud?
It's not really a cloud at all, but rather refers to the trillion or so comets thought to orbit the Sun at great distances.
What's unusual about our Moon?
It's surprisingly large relative to the planet it orbits.
Correct definition of kinetic energy?
Kinetic energy is the energy an object has due to its motion. Two examples are a car driving down the highway or the movements of the molecules of liquid in a cup of hot coffee.
Which forms of light are lower in energy and frequency than the light that our eyes can see?
infrared and radio
As shown in the video, Earth has two tidal bulges at all times. Approximately where are these bulges located?
One faces the Moon and one faces opposite the Moon. *The tidal bulges face toward and away from the Moon, because they are caused primarily by the gravitational attraction between Earth and the Moon. Friction explains why the bulges are slightly ahead of the Earth-Moon line, rather than directly on the Earth-Moon line. We'll ignore that detail for now.
Correct definition of potential energy?
Potential energy is energy that is stored. Two examples of potential energy are breakfast cereal, which has chemical potential energy, and a heavy book on the top shelf at the library, which has gravitational potential energy.
Correct definition of radiative energy?
Radiative energy is energy in light. Sunlight carries this form of energy, as do other forms of light including X-rays and radio waves.
When a rock is held above the ground, we say it has some potential energy. When we let it go, it falls and we say the potential energy is converted to kinetic energy. Finally, the rock hits the ground. What has happened to the energy?
The energy goes to producing sound and to heating the ground, rock, and surrounding air.
The video shows a collapsing cloud of interstellar gas, which is held together by the mutual gravitational attraction of all the atoms and molecules that make up the cloud. As the cloud collapses, the overall force of gravity that draws the cloud inward gradually becomes stronger because the strength of gravity follows an inverse square law with distance.
The force of gravity between any two particles increases as the particles come closer together. Therefore, as the cloud shrinks and particles move closer together, the force of gravity strengthens. This will tend to accelerate the collapse as long as no other force resists it. This is the case during the early stages of the collapse before the internal gas pressure builds up. (Once the gas pressure builds up, the outward push of the pressure can counteract the inward pull of gravity, which is why the cloud eventually stops contracting.)
One tidal bulge faces toward the Moon because that is where the gravitational attraction between Earth and the Moon is strongest. Which of the following best explains why there is also a second tidal bulge?
The second tidal bulge arises because gravity weakens with distance, essentially stretching Earth along the Earth-Moon line. *Tides are created by gravity, and the tidal force is caused by the fact that gravity weakens with distance. Therefore, the parts of Earth that are closer to the Moon feel a stronger gravitational attraction to the Moon, and the parts of Earth that are farther away feel a weaker gravitational attraction to the Moon. This varying gravitational attraction essentially stretches Earth along the Earth-Moon line, creating tidal bulges on both sides.
Which of the following statements correctly describes the law of conservation of energy?
The total quantity of energy in the universe never changes.
Suppose you heat up an oven and boil a pot of water. Which of the following explains why you would be burned by sticking your hand briefly in the pot but not by sticking your hand briefly in the oven?
The water has a higher heat content than the oven because of density.
According to the nebular theory, what are asteroids and comets?
They are leftover planetesimals that never accreted into planets.
Suppose you watch a leaf bobbing up and down as ripples pass it by in a pond. You notice that it does two full up and down bobs each second. Which statement is true of the ripples on the pond?
They have a frequency of 2 hertz.
Based on the nebular theory as it explains our own solar system, which of the following should we expect to be true for other star systems?
We expect all solar systems to form in similar ways from collapsing gas clouds and therefore to share basic features, such as the planets all orbiting in the same direction and nearly the same plane. We also expect planets to form similarly through accretion, with planets that form near a star tending to be terrestrial in nature and planets that form farther away tending to be jovian; however, as you'll learn in later chapters, the details of planetary formation allow for additional types of planets beyond just those two categories. We do not expect particulars that are probably coincidental, such as the precise numbers of planets, to be the same in different solar systems.
Choose the correct description of what do we mean when we say that light is an electromagnetic wave and the relationship among wavelength, frequency, and speed for light waves.
We say that light is an electromagnetic wave because light is a oscillation of electric and magnetic fields. frequency=speed of light/wavelength
Which of the following scenarios correctly demonstrates the transformation of mass into energy as given by Einstein's equation, E = mc2?
When hydrogen is fused into helium, whether in the Sun or in a nuclear bomb, the mass difference is turned into energy.
Which object has the most kinetic energy? -a 3-ton truck moving 70 km/hr -a 1-ton truck moving 110 km/hr -a 2-ton truck moving 90 km/hr -a 4-ton truck moving 50 km/hr -A, B, C, and D all have the same kinetic energy.
a 2-ton truck moving 90 km/hr
Giant-Impact Hypothesis
a mars sized body impacts the Earth, causing an equal mass to be ejected; the moon *Note the importance of the combination of modeling and observations. Models help us understand what conditions must have been like in the early solar system, showing that there must have been a great many leftover planetesimals, some large enough to cause giant impacts. Observations of the Moon's composition show that it is consistent with formation in a giant impact, which would have led to have a composition similar to Earth's mantle (because it formed from material blasted out of Earth's outer layers) and low in easily vaporized ingredients (because these ingredients would have remained gaseous and therefore would not have participated in the Moon's accretion).
What is the Kuiper belt?
a region of the solar system beginning just beyond the orbit of Neptune that contains many icy comets.
Where would you expect terrestrial planets to form in the solar nebula?
anywhere between the innermost regions (within about the inner 0.3 AU) and the frost line *Terrestrial planets are made mostly of metal and rock and therefore formed in the region in which it was cool enough for metal and rock to condense but still too warm for hydrogen compounds to condense into ices. This means the region between the innermost regions (within about the inner 0.3 AU) and the frost line.
You have found that tides on Earth are determined primarily by the position of the Moon, with the Sun playing only a secondary role. Why does the Moon play a greater role in causing tides than the Sun?
because the gravitational attraction between Earth and the Moon varies more across Earth than does the gravitational attraction between Earth and the Sun *The Sun exerts a stronger gravitational force on Earth, which is why Earth orbits the Sun. However, tides are caused by the variation in the gravitational attraction across Earth. Even though the gravitational attraction between Earth and the Moon is smaller than the attraction between Earth and the Sun, the Moon's much closer distance makes this attraction vary more across Earth. That is why tides are due primarily to the Moon, with only a secondary effect from the Sun.
an apple contains ____ energy that your body can convert into other forms of energy
chemical potential
Based on our current theory of Earth's formation, the water we drink comes from:
comets that impacted Earth.
Which of the following is a form of electrical potential energy? -moving blades on an electric mixer -energy from the Sun -light from a fluorescent bulb -energy coming to your house from power companies -coal
energy coming to your house from power companies
As an interstellar gas cloud shrinks in size, its gravitational potential energy:
gradually transforms into other forms of energy.
an asteroid that is moving farther from the sun is gaining ____ energy
gravitational potential energy
Compared to red light, blue light has higher frequency and -
higher energy and shorter wavelength than red light.
As a giant cloud of gas collapses due to gravity, you would expect its rate of rotation to:
increase
The amount of gravitational potential energy released as an object falls depends on:
its mass and the distance it falls, as well as the rate of gravitational acceleration.
Suppose you know the frequency of a photon and the speed of light. What else can you determine about the photon?
its wavelength and energy
Which of the following is NOT a unit of energy?
kilowatt
Rapidly moving comets have more ______ energy than slowly moving ones.
kinetic
Red light has a _____ wavelength and a _____ frequency than does blue light.
longer, lower *Red light has a wavelength of about 700 nm, which is longer than the 400-nm wavelength of blue light. As explained in the video, longer wavelength means lower frequency for light.
Nuclear fusion in stars converts some of the ________-energy of hydrogen nuclei into light and heat
mass
The ultimate source of energy that powers the Sun is:
mass energy of hydrogen fusing into helium.
Newton's second law of motion tells us that the net force applied to an object equals its:
mass times acceleration.
Momentum is defined as:
mass times velocity
What quantities does angular momentum depend upon?
mass, velocity, and radius
Vaporization is the process in which:
molecules go from the solid phase to the gas phase.
Now consider why the observed patterns of motion lead to the conclusion that the planets were not born in separate, random events. The reason for this conclusion is that, if the planets had been born in separate, random events, we would expect that __________.
planetary orbits would have many different orientations and directions, rather than all being in the same direction and in the same plane
Which of the following is not a conserved quantity? -energy -radiation -angular momentum -momentum
radiation
The light from Polaris travels through space in the form of ____________ energy.
radiative
If you have a telescope that is observing light with wavelengths of a few meters, you are observing __________.
radio waves
The jovian planets are thought to have formed as gravity drew hydrogen and helium gas around planetesimals made of __________.
rocks, metals, and ices *Because ices could condense only beyond the frost line, we expect jovian planets to form only beyond the frost line. Note that many extrasolar planets appear to be jovian but are located close to their stars, leading scientists to suspect that these planets migrated inward after originally forming beyond the frost lines of their star systems.
What substances were found in the innermost regions (within about the inner 0.3 AU) of the solar system before planets began to form?
rocks, metals, hydrogen compounds, hydrogen, and helium, all in gaseous form
The heavy bombardment phase of the solar system lasted:
several hundreds of millions of years.
Consider Earth and the Moon. As you should now realize, the gravitational force that Earth exerts on the Moon is equal and opposite to that which the Moon exerts on Earth. Therefore, according to Newton's second law of motion __________.
the Moon has a larger acceleration than Earth, because it has a smaller mass
Compared to its angular momentum when it is farthest from the Sun, Earth's angular momentum when it is nearest to the Sun is:
the same
Suppose that two objects collide. Which of the following things is NOT the same both before and after the collision? -the total momentum of the objects -the total energy of the objects -the total angular momentum of the objects -the total temperature of the objects
the total temperature of the objects
Due to its much higher density, water heated to 80 degrees (Celsius) contains more ______ energy than air at the same temperature.
thermal
Any particular location on Earth experiences __________.
two high tides and two low tides each day
