AST_101_Lesson_3_Homework (1)
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Arizona State University, Tempe *
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101
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Astronomy
Date
Feb 20, 2024
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Uploaded by ProfessorSheep4002
AST 101 Lesson 3 Homework
Student Name: Isabella Brown
Question 1 (6 points 2 points each) Briefly describe the most significant scientific contributions of the following people:
A)
Kepler
Kepler is most known for his three laws of planetary motion, which later brought about celestial mechanics. Another one of his important findings was that planets move in elliptical orbits and at different speeds, times and placement. His role in science was very important for the scientific revolution. B)
Tycho
Tycho Brahe contributed to the scientific community by developing astronomical instruments and recording data on stars. His work is most accurate for a time period before telescopes. He mapped the stars in the sky, as well as our solar system. C)
Newton
Issac Newton, was a pivotal figure in the scientific revolution. He is credited with the discovery of the composition of white light. This discovery paved the way for modern physical optics. He formulated the three laws of motion, which are fundamental principles of modern physics. He is also credited with establishing the law of universal gravitation and the first discovery of infinitesimal calculus. Question 2 (6 points, 2 points each): Describe Kepler's Three Laws of Motion in your own words
. In your answers, use complete sentences and good grammar.
A)
Kepler's First Law:
Planets move in elliptical orbits with the Sun at one of the two foci, not a perfect circle. The Sun is slightly offset from the center of the ellipse. This law was a significant shift from the prior belief
of circular orbits. B)
Kepler's Second Law:
A line connecting the sun and a planet sweeps out equal areas in equal times, meaning planets move faster when they are closer to the Sun and slower when they are farther away. This law explains the variations in a planet's speed throughout its orbit. C)
Kepler's Third Law:
The square of a planet's orbital period is proportional to the cube of its semi-major axis, meaning the further a planet is from the Sun, the longer it takes to complete its orbit. This law allows us to predict a plants orbital period if its distance from the Sun is known. Page 1 of 3
AST 101 Lesson 3 Homework
Question 3 (5 points): Consider a body moving in a perfectly circular
path at a constant speed. Are there forces acting in such a system? How do you know?
Yes, there are forces acting on a body moving in a perfectly circular path at a constant speed. This is due to Newtons first law of motion, which states that an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by a unbalanced force. In a circular path, the direction of motion of the object is constantly changing even if the speed is constant. Therefore, there must be a force acting towards the center of the circle causing this change in direction. Question 4 (5 points): Suppose the Sun shrunk from its current diameter to 1/10 its current diameter, but its mass remained the same. What would happen to the Earth's orbit?
A)
The length of a year would decrease to 1/10 as long.
B)
The length of a year would decrease to 1/100 as long.
C)
The length of a year would increase to 100 times as long.
D)
The length of the year would not change.
E)
There is not enough information to answer this question.
Answer: D
Question 5 (5 points): By what factor would a person's weight increase if the Earth had 10 times
its present mass but the same volume? Explain your reasoning or show your calculations
.
Answer: A person's weight would increase by a factor of 10 if the earth had 10 times its present mass but the same volume. This is because weight is the force of gravity acting on an object, which is given by the formula F=Gm1m2/r2. The increase in weight is directly proportional to the
increase in the earth's mass. Question 6 (4 points): Explain how two atoms with a different number of neutrons in their nucleus can be the same element.
Two atoms can be the same element even if they have a different number of neutrons because the identity of an element is determined by the number of protons in its nucleus, not neutrons. This number of protons is known as the atomic number. Atoms of the same element with different numbers of neutrons are called isotopes. Question 7 (6 points): Using the concepts of waves and wavelength, explain how the principle of
the Doppler Shift allows us to calculate the radial velocity of an object emitting light.
The Doppler Shift refers to the change in frequency or wavelength of a wave in relation to an observer moving relative to the wave source. When an object emitting light moves towards or away from an observer, the light waves it emits are compressed or stretched, respectively, leading to a shift in observed wavelength and frequency. By measuring this shift, known as redshift or blueshift, and can calculate speed. Page 2 of 3
AST 101 Lesson 3 Homework
Question 8 (8 points): Explain how electrons use light energy to move among energy levels within an atom. In your answer, include the following terms: emit or emission, absorb or absorption, and photon.
In an atom, electrons reside at specific energy levels. When a photon, which is a particle of light energy, is absorbed by an electron, the electron gains energy and moves to a higher energy level. Conversely, when an electron drops from a higher energy level to a lower one, it emits a photon and loses energy. This process of absorption and emission allows electrons to move among different energy levels within an atom. Question 9 (5 points): Suppose a star's continuous spectrum peaks at a wavelength of 600 nm. Calculate the temperature of this star.
Answer: 2.8977719 mm • K = 4830K Question 10 (10 points): Explain how the spectrum of light from an object shows a "fingerprint" that permits us to determine the elements or chemical compounds in its composition.
The spectrum of light from an object can reveal its chemical composition due to a phenomenon knwon as atomic emission or absorption spectra. Each element or compound has a unique set of energy levels, and when electrons transition between these levels, they emit or absorb light at
specific wavelengths. These wavelengths form a unique pattern or “fingerprint” in the light spectrum for each element or compound. By analyzing these patterns in the spectrum of light from an object, scientists can identify the elements or compounds present. This principle is widely used in fields like astronomy to determine the composition of distant stars and galaxies. Page 3 of 3
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