Selected answers for Lecture-tutorials
- Position - page 1
- 1. Imaginary
- 2. No. Earth blocks downward line of sights.
- 3. A, pos 4
- 4. Rising
- 5. Setting
- 6. 3
- 7. None
- 9. f) B1 northeast high
- 9. i) B4 north low
- Motion - page 3
- 3. approx. overhead
- 4. zenith (roughly) coincides with star B, pos 1, the 6 am position.
- 5. high in the south
- 7. Star A rises at a right-leaning angle compared to vertical
- 9. downward
- 11. Student 2 is correct
- Seasonal Stars - page 7
- 1. Taurus is high, south
- 2. Eastward of Taurus is Gemini. Westward of Taurus is Aries.
- 3. midnight
- 4. 6 hours after midnight is 6 a.m., approximately sunrise. The sun rises in the east. [More subtly, the drawn configuration is north hemisphere winter, so the sun will rise in the NE and it will rise later than 6 a.m.]
- 5. Scorpius
- 6. Scorpius
- 7. Gemini
- 8. west
- 9. earlier by 24/12 = 2 hours
- 10. Betelgeuse will rise about 4 minutes earlier each night, compared with the night before.
- Kepler's 2nd law - page 21
- 2. Speed is constant, and a planet-sun line sweeps out equal areas in equal times.
- 4. Several correct configurations are possible, but at leasat one letter must be skipped. Example: triangle e-sun-f sweeps out too little area compared with triangle b-sun-a.
- 5. If the areas are equal, the time interval must also be equal.
- 7. Near the sun, the planet travels faster.
- 8. No.
- 9. Slowest far from the sun, fastest near the sun, judging by spacing of the position-dots.
- 10. Planet speed is increasing. (It is "falling into" the sun at that point.)
- 11. Planets travel faster when near their star.
- 12. a
- 13. Orbit a exhibits uniform circular motion. Orbit c has the largest contrast in orbital speeds.
- 14. With an orbital eccentricity of only 0.01, earth's speed changes almost not at all.