Astronomy 4.4-5.3
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.
The following diagrams are the same as those from Part A. This time, rank the pairs from left to right based on the size of the acceleration the asteroid on the left would have due to the gravitational force exerted on it by the object on the right, from largest to smallest.
According to Newton's second law, the asteroid with the largest acceleration will be the one that has the strongest gravitational force exerted on it by the object on the right. That is why the ranking here is the same as the ranking for Part A.
If you actually performed and compared the two trials chosen in Part C, you would find that, while the basketball and marble would hit the ground at almost the same time, it would not quite be exact: The basketball would take slightly longer to fall to the ground than the marble. Why?
Because air resistance has a greater effect on the larger ball.
The following five diagrams show pairs of astronomical objects that are all separated by the same distance d. Assume the asteroids are all identical and relatively small, just a few kilometers across. Considering only the two objects shown in each pair, rank the strength, from strongest to weakest, of the gravitational force acting on the asteroid on the left.
Because the distance is the same for all five cases, the gravitational force depends only on the product of the masses. And because the same asteroid is on the left in all five cases, the relative strength of gravitational force depends on the mass of the object on the right. Continue to Part B to explore what happens if we instead ask about the gravitational force acting on the object on the right.
Assume you have completed the two trials chosen in Part A. Which of the following possible outcomes from the trials would support Newton's theory of gravity? Neglect effects of air resistance
Both balls fall to the ground in the same amount of time
Choose the correct definition of electrical charge.
Electrical charge is a measure of how strongly something will interact with electromagnetic fields
midpoint- Rank the five positions of the spaceship from left to right based on the strength of the gravitational force that Earth exerts on the spaceship, from strongest to weakest
Gravity follows an inverse square law with distance, which means the force of gravity between Earth and the spaceship weakens as the spaceship gets farther from Earth
notice that the size of the tidal bulges varies with the Moon's phase, which depends on its orbital position relative to the Sun
High tides are highest at both full moon and new moon. Low tides are lowest at both full moon and new moon.
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.
Which statement must be true in order for a rocket to travel from Earth to another planet?
It must attain escape velocity from Earth.
Why is a sunflower yellow?
It reflects yellow light.
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
Emission
Light comes from a light bulb. Light comes from your computer screen.
Again considering only the two objects shown in each pair, this time rank the strength, from strongest to weakest, of the gravitational force acting on the object on the right.
Newton's third law tells us that the gravitational force exerted on the asteroid on the left by the object on the right will be equal in magnitude, but opposite in direction to the gravitational force exerted on the object on the right by the asteroid on the left. That is why the ranking here is the same as the ranking for Part A.
Approximately where is it currently high tide on Earth?
On the portion of Earth facing directly toward the Moon and on the portion of Earth facing directly away from the Moon.
Earth has two tidal bulges at all times. Approximately where are these bulges located?
One faces the Moon and one faces opposite the Moon
Reflection or scattering
Red light hits a red sweatshirt. White light hits a white piece of paper.
Einstein's theory, like Newton's, predicts that, in the absence of air resistance, all objects should fall at the same rate regardless of their masses. Consider the following hypothetical experimental results. Which one would indicate a failure of Einstein's theory?
Scientists dropping balls on the Moon find that balls of different mass fall at slightly different rates.
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
you wish to test how the size of an object affects the rate of its fall. Which pair of trials should you compare?
The variable of interest is now size, so appropriate trials to compare are those in which size differs but other variables are constant
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
Which of the following best describes the fundamental difference between two different chemical elements (such as oxygen and carbon)?
They have different numbers of protons in their nucleus.
There are more atoms in a glass of water than stars in the observable universe.
True
Absorption
Visible light does not pass through a black wall. Blue light hits a red sweatshirt.
electron and a proton or two electrons attracting or repelling one another
We define a proton as having +1 unit of charge and an electron as having -1 unit when talking about atoms and particles. Two particles with charges of different sign will attract each other, so protons and electrons will attract. Particles with charges of the same sign will repel each other, so two electrons will repel each other.
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
What if the ranking is done for the wavelengths of the different forms of light (shortest to longest, left to right)
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.
Which of the following are forms of light (electromagnetic radiation)?
X rays infrared ultraviolet gamma rays radio waves visible light microwaves
Do tides also affect land?
Yes, though land rises and falls by a much smaller amount than the oceans
The following diagrams show five pairs of asteroids, labeled with their relative masses (M) and distances (d) between them. For example, an asteroid with M=2 has twice the mass of one with M=1 and a distance of d=2 is twice as large as a distance of d=1. Rank each pair from left to right based on the strength of the gravitational force attracting the asteroids to each other, from strongest to weakest.
You have correctly taken into account both the masses of the asteroids and the distances between them.
At extremely high temperatures (e.g., millions of degrees), which of the following best describes the phase of matter?
a plasma consisting of positively charged ions and free electrons
If the Moon were closer to Earth, high tides would:
be higher than they are now.
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
As the cloud collapses, the overall force of gravity that draws the cloud inward gradually _____ because the strength of gravity follows--
becomes stronger an inverse square law with distance
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
Compared to red light, blue light has higher frequency and
higher energy and shorter wavelength than red light.
Which forms of light are lower in energy and frequency than the light that our eyes can see?
infrared and radio
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
Radio waves are:
light
Red light has a _____ wavelength and a _____ frequency than does blue light.
longer, lower
Vaporization is the process in which
molecules go from the solid phase to the gas phase.
Suppose that you had "X-ray vision" that allowed you to see X rays. What would you notice when you looked at a friend standing near you that you could not notice with your visible light vision alone?
nothing
If Earth were twice as far from the Sun, the force of gravity attracting Earth to the Sun would be:
one-quarter as strong.
If you have a telescope that is observing light with wavelengths of a few meters, you are observing __________
radio waves
List the different forms of light in order from highest to lowest energy.
radio, infrared, visible, ultraviolet,X rays, gamma rays RIV UXG
X ray photons have a _____ wavelength, _____ frequency, and _____ energy than do ultraviolet photons.
shorter, higher, higher
As the cloud shrinks in size, its rate of rotation BLANK because its total angular momentum is BLANK
speeds up conserved.
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
Any particular location on Earth experiences __________.
two high tides and two low tides each day
The following diagrams are the same as those from Part A. This time, rank the five positions of the spaceship from left to right based on the strength of the gravitational force that the Moon exerts on the spaceship, from strongest to weakest.
Gravity follows an inverse square law with distance, which means the force of gravity between the Moon and the spaceship increases as the spaceship approaches the Moon. Now continue to Part C for activities that look at the effects of both distance and mass on gravity.
As the cloud shrinks in size, its central temperature __________ as a result of its __________.
INCREASES gravitational potential energy being converted to thermal energy
Transmission
Visible light meets clear glass .Cell phone signals pass through walls
testing that object's mass does not affect its rate of fall?
compare the results of two trials that are identical except for the mass of the balls. In the language of experimental design, we say that the mass is the "variable of interest" for this experiment, and we therefore hold the other variables (size and height) constant so that they cannot affect the results.
