an atom of the element iron an atomic number of 26, and an atomic weight of 56. If it is neutral, how many protons, neutrons, and electrons does it have?
26 protons, 26 electron, and 30 neutrons
at which lunar phase are tides least pronounced (lowest tide)?
first and third quarter moons
at which lunar phase are tides most pronounced (highest tide)?
full moon and new moon
a skater can spin faster by pulling in her arms closer to her body or spin slower by spreading her arms out from her body. This is due to?
conservation of angular momentum
what is meant by occam's razor
the idea that scientists should prefer the simpler of two models that agree equally well with observations
changing the orbit of a spacecraft by firing thrusters is an example of
Newton's 3rd Law of Motion
why do we have seasons on Earth
As the Earth goes around the Sun and the Earth's axis remains pointed toward the North Celestial Pole, the Northern and Southern hemispheres alternately receive more and less direct sunlight.
when white light passes through a cool cloud of gas, we see
an absorption line spectrum
suppose you see two stars: a blue star and a red star. Which of the following can you conclude about the two stars? Assume that no Doppler shifts are involved.
the blue star has the hotter surface than the red star.
the force of gravity is an inverse square law. This means that, if you double the distance between two large masses, the gravitational force between them
weakens by a factor of 4
what causes a star to twinkle
bending of light rays by turbulent layers in the atmosphere
kepler's second law, which states that as a planet moves around its orbit it sweeps out equal areas in equal times, means that
a planet travels faster when it is nearer to the Sun and slower when it is farther from the Sun.
what do scientists mean by verifiable observation
statements that a person can, in principle, verify for himself or herself
what is meant by scientific paradigm
a generally well established scientific theory or set of theories
which of the following wavelength regions cannot be studied with telescopes on the ground
ultraviolet and x rays
which of the following has your "address" in the correct order
you, Earth, solar system, Milky Way, Local Group, Local Supercluster
which of the following statements about thermal radiation is always true
a hot object emits photon with a higher aerage energy than a cool object
which of the following statements about x rays and radio waves is not true
Neither X rays nor radio waves can penetrate Earth's atmosphere
what quantities does angular momentum depend upon
mass, velocity and radius
if the moon is setting at noon, the phase of the moon must be
what conditions are required for a solar eclipse
the phase of the moon must be new, and the moon's orbital plane must lie in the eliptic
which of the following statements about the scientific theories is not true
--A theory cannot be taken seriously by scientists if it contradicts other theories developed by scientists over the past several hundred years
which scientists played a major role in overturning the ancient idea of an Earth-centered universe, and about when?
Copernicus, Kepler, and Galileo; about 400 years ago
which of the following is not an advantage of the hubble space telescope over ground-based telescopes
It is closer to the stars
how did Eratosthenes estimate the size of the earth in 240 B.C.
by comparing the maximum altitude of the Sun in two cities at different latitudes
Which of the following statements does not use the term light-year in an appropriate way
It will take you light-years to complete this assignment
suppose an object is moving in a straight line at 50 mi/hr. According to Newton's first law of motion, the object will
continue to move in the same way until it is acted upon by a force
Newton's second law of motion tells us that the net force applied to an object equals its
mass times acceleration
When an atom absorbs a photon containing energy, any of the following can happen except which
An electron moves from an upper energy level to a lower one
what does the technique of interferometry allow
It allows two or more telescopes to obtain the angular resolution of a single telescope much larger than any of the individual telescopes.
how can an electron in an atom lose energy to go from a higher energy level to a lower energy level
it releases a photon equal in energy to its own energy drop
we can learn a lot about the properties of a star by studying its spectrum. All of the following statements are true except one. Which one?
The total amount of light in the spectrum tells us the star's radius
according to what we now know from Newton's laws, which of the following best explains why Kepler's second law is true
A planet's total orbital energy must be conserved as it moves around its orbit
what is a circumpolar star?
a star that always remains above your horizon
the names of the seven days of the week are based on the
seven planets closest to the Sun
at extremely high temperatures, which of the following best describes the phase of matter
a plasma consisting of positively charged ions and free electrons
the frequency of a wave is
measured in cycles per second. b)measured in hertz (Hz). c)equal to the speed of the wave divided by the wavelength of the wave. d)the number of peaks passing by any point each second. e)all of the above
the spectra of most galaxies shows redshifts. This means their spectral lines
have wavelengths that are longer than normal Rate This Answer
Radiative energy is
if one object has a large redshift and another object has a small redshift, what can we conclude about these two objects?
The one with the large redshift is moving away from us faster than the one with the small redshift
what is an astronomical unit
the average distance from the earth to the Sun
when an atom loses an electron, it becomes
kepler's third law, means that
a planet's period does not depend on the eccentricity of its orbit. B) all orbits with the same semimajor axis have the same period. C) the period of a planet does not depend on its mass. D) planets that are farther from the Sun move at slower average speeds than nearer planets. E) All of these are correct.
which of the following best describes the milky way galaxy?
a spiral galaxy with a disk about 100,000 light-years in diameter and containing between 100 billion and 1 trillion stars
considering Einstein's famous equation E=mc2, which of the following statements is true
A small amount of mass can be turned into a large amount of energy
from lowest energy to highest energy, which of the following correctly orders the different categories of electromagnetic radiation
radio, infrared, visible light, ultraviolet, X rays, gamma rays
how are wavelength, frequency, and energy related for photons of light
Longer wavelength means lower frequency and lower energy
how did the Ptolemaic model explain the apparent retrograde motion of the planets?
The planets moved along small circles that moved on larger circles around the Earth
what causes the apparent retrograde motion of the planets
As Earth passes another planet, the other planet appears to move backward with respect to the background stars, but the planet's motion does not really change.
energy and power are different words for the same thing
if you are driving at 30 miles per hour and increase your speed to 60 miles per hour, you quadruple your kinetic energy
x rays, because they have more energy, travel through space faster than visible light
grass is green because it absorbs green light, reflecting all other colors
the seasons on Earth are caused by its elliptical orbit around the sun
the moon is constantly falling toward the earth
doubling the distance between two objects halves the gravitational force between them
colombus was the first person to discover that the earth was round
scientific theories can never be proved beyond a reasonable doubt