ISP205, Sec 3, Midterm 1

ISP205, Section 3, Hufnagel & Stein

EXAM 1, The Sky

                                        Name: ________________________


                                        Student Number: ______________

SIT in the seat corresponding to the SEAT NUMBER ON THE EXAM.
If you answer on the exam, leave that question blank on the bubble sheet.
Do the easiest questions first.
If you have the slightest doubt about what a question is asking -- ask a proctor.
If you feel no choice for answers to a question are correct, write what you think is the correct answer and note the question number on this page.
Do NOT open the exam until it is time to start.
DON'T PANIC! GOOD LUCK!

Although everyone was asked the same questions, the order of the questions and the order of the answers was different for the different versions.

(3 pts) Select the best description which describes how scientific models are tested.
1. Test consistency of the model with other scientific theories.
2. Compare the model's predictions with previously known observations.
3. Compare the model's predictions with new observations.
4. The model is the simplest one, consistent with the principle of Occam's Razor.
5. none of these
(3 pts) When Newton used his theory of motion and gravity to predict the acceleration of the Moon and then compared it with the observed acceleration of the Moon, this was what stage in the development of his theories of motion and gravity?

Testing the theory.
(3 pts) Suppose you are able to hitch a ride on Comet Hale-Bopp, which is currently approaching the Sun on its highly elliptical orbit around the Sun. In 1000 years, Comet Hale-Bopp will be farther away from the Sun than Pluto. In 2000 years from now, Comet Hale-Bopp will return to the same position in its orbit near the Sun. Where will it spend most of these 2000 years, inside or outside the orbit of Jupiter?
1. Outside the orbit of Jupiter, because Kepler's Law says it will travel more slowly on the outer part of its orbit.
2. Inside the orbit of Jupiter, because the Sun's gravity is stronger there.
3. Its time will be evenly split, as its semi-major axis is exactly the same distance as Jupiter's orbit.
4. Outside the orbit of Jupiter, because the extreme mass of Jupiter will perturb its orbit as it goes by.
5. Inside the orbit of Jupiter, because we only detect comets when they come close enough to the Sun and it starts to melt them.
(5 pts) Explain why the weeks are not shorter in the winter even though there are fewer hours of daylight.

A day is always 24 hours long. Although there are fewer hours of daylight in winter there are more hours of darkness. A week has seven days and hence the same number of hours all year round.
(3 pts) The Moon and the Earth are attached to each other by their mutual gravitational attraction. Suppose our Moon had twice the amount of mass, but was still the same distance away. How would this effect its gravitational force on the Earth? (F=GMm/D²)
1. This would halve the amount of gravitational force.
2. This would quadruple the amount of gravitational force.
3. This would double the amount of gravitational force.
4. This would decrease the amount of gravitational force by one-quarter.
5. Since the force is mutual, there would be no net change in the gravitational force.
(5 pts) One of the predictions of the Copernican Model of the Solar System was that the Earth orbits around the Sun. Explain why the Moon stays in orbit around the Earth, even though the Earth is moving around the Sun.

Newton's Law of Gravity explains that the Moon and the Earth are attracted to each other by the force of gravity. This force is directly proportional to the product of their masses, and inversely proportional to the square of their distance apart. Since the Moon is much closer to the Earth than to the Sun, the attraction to the Earth dominates and holds it in orbit about the Earth.
(3 pts) The Moon rises in the
1. east.
2. west.
3. north.
4. south.
5. It could be any of these.
(3 pts) With respect to the stars, the Moon moves toward the
1. east.
2. west.
3. north.
4. south.
5. It depends on the phase of the Moon.
(3 pts) In the Ptolemaic model of the Solar System, which of the following explains why retrograde motion of other planets is observed?
1. All of the planets are orbiting around the Earth.
2. The ancient Greeks were not aware of retrograde motion, so their model didn't have to explain it.
3. When the slower inner planet ``laps'' a faster outer planet, it looks like the outer planet moves backward.
4. The Earth itself is not moving.
5. The planets are moving on epicycles, which are centered on the deferent.
(3 pts) With respect to the stars, Saturn's usual apparent motion is toward the
1. east.
2. west.
3. north.
4. south.
5. it depends on which constellation its in.
(3 pts) The star Betelgeuse has coordinates RA 5 hours 50 minutes (Right Ascension) and Dec 7 degrees 23 min (Declination). The star Altair has RA 19 hours 46 minutes and Dec 8 degrees 36 mins. Which star is farther south?
1. They are the same.
2. Betelguese
3. Altair
4. There is not enough information.
(5 pts) Draw the positions the of Earth, Mars and the Sun when Mars is undergoing retrograde motion. Their sizes and distances need not be to scale.

See Figure 5-12 in the Textbook.
(3 pts) When Johannes Kepler produced a model showing that Mars moved with non-uniform speed in its orbit, which model or models did this disprove?
1. Ptolemaic, Copernican, and Keplerian
2. Ptolemaic
3. Copernican
4. Ptolemaic and Copernican
5. Keplerian
(3 pts) Why did Kepler change Copernicus' heliocentric model to one in which the planets moved on elliptical orbits with varying speeds?
1. To solve a problem: the observations of Tycho Brahe were inconsistent with Copernicus model.
2. For aesthetic reasons: to make a simpler model than Copernicus.
3. For philosophical reasons: to get away from the Ptolemaic insistence on uniform circular motion.
4. To explain the orbits of Jupiter's moons found by Galileo.
5. None of these.
(3 pts) Which of the following planets can be observed to undergo retrograde motion?
1. Mars
2. Jupiter
3. Saturn
4. Venus
5. All of these
(3 pts) You see the full Moon high above the horizon as you look toward the south. What is the time of day?
1. midnight
2. dawn
3. noon
4. sunset (or dusk)
5. There is not information to determine what time of day.
(3 pts) You are facing west on Michigan Ave at midnight and see the Moon just above the horizon What is the phase of the Moon?

First Quarter
(3 pts) When we say a car goes from standing still to 70 mph in 5 seconds, we are describing its
1. velocity
2. acceleration
3. mass
4. energy
5. force
(3 pts) Describe why you can stop a runaway child's bicycle but not a locomotive.

The mass of a railway locomotive is much greater than the mass of the child's bicycle. It thus takes a much greater force to decelerate a locomotive than a bicycle.
(3 pts) Which of the following describes acceleration
1. As a planet orbits around the Sun, its direction of motion changes.
2. As a planet orbits around the Sun, its distance from the Sun changes.
3. As a planet orbits around the Sun, it moves toward the east with respect to the stars.
4. As a planet orbits around the Sun, it undergoes retrograde motion.
5. As a planet orbits around the Sun, its mass does not change.
(3 pts) On the diagram below showing the Sun, Earth and orbit of the Moon, draw the position of the Moon during a solar eclipse.

See Figure 4-25 in the Texbook.
(3 pts) On the diagram below showing the Sun and the Earth at various positions in its orbit, which is the position of the Earth during summer in Michigan?
1. (1)
2. (2)
3. (3)
4. (4)
5. It could be any of these, depending on where the Earth is closest to the Sun in its orbit.
(3 pts) It takes about one _______ for the Moon to orbit around the Earth once.
1. year
2. day
3. month
4. hour
5. week
(3 pts) Which fundamental idea of the Ptolemaic and Copernican models did Galileo disprove when he saw sunspots on the Sun?
1. The heavens are perfect.
2. All heavenly bodies move in perfect circles.
3. The Sun is stationery and doesn't spin on its axis.
4. All heavenly bodies move at a uniform speed.
5. The Earth is at the center of the Solar System (geocentric).
(3 pts) The most revolutionary concept in Copernicus' model of the Solar System was:
1. the Earth moves.
2. the Earth spins on its axis.
3. the Earth is not the center of the Solar System.
4. the orbit of the Earth is an ellipse with the Sun at one focus.
5. the speed of the Earth in its orbit around the sun changes.
(3 pts) Astronomers have now found some planets orbiting around other stars. Suppose they see a planet orbit around a star at twice the distance of the Earth from the Sun with a period of 2 years. What is the mass of that star? You can use whichever of the following equations will solve this problem best:
F = ma, P²=a³, m₁ + m₂ = D³/P², E = m c²
You need to use Kepler's third law in the form that includes the masses of the orbiting bodies:

M₁ + M₂ [mass in units of M_sun]
= D[distance in units of AU]³/P[period in units of years] ²
In this case, one mass is that of the star and the other mass is that of the planet, which is much smaller than the mass of the star and hence can be neglected in comparison to the star's mass. Then
M_star [M_sun] = (2 [AU])³ / (2 [yrs])²
= 8 / 4 = 2 M_sun (2 solar masses)
(3 pts) The Hubble Space Telescope orbits the Earth at a height of 300 miles above the surface of the Earth. What keeps it from falling back to Earth?
1. Earth's gravity.
2. Its distance from Earth.
3. Its orbital motion.
4. The anti-gravity generator.
5. There is no gravity in space.
(3 pts) The show ``Travelers Through the Solar System'' told the story of the discovery of active volcanos on only one other astronomical body other than Earth. That body is:
1. the Moon
2. Mars
3. Io
4. Venus
5. Mercury
(3 pts) The mass of the Earth can be determined by using
1. The size and period of the Earth's orbit around the Sun.
2. The size and period of the Moon's orbit around the Earth.
3. The size and speed of the Earth in orbit around the Sun.
4. The Earth--Sun distance, combined with the Sun's mass.
5. The Earth--Moon distance, combined with the Moon's mass.
On the sky map for April below draw small circles around as many of the stars from your list of 16 brightest northern hemisphere stars as you can find and write their names next to each such star. [One point for each correct star, but minus 1/2 point for each incorrect star, so don't guess.]

{ Updated: 1997.02.19 (Wednesday) 21:00:32 EST }
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Beth Hufnagel's home page, email: hufnage4@pilot.msu.edu

Bob Stein's home page , email: steinr@pilot.msu.edu