Question

scientists have studied the orbits of different planets. venus has a very circular orbit, while mars has a more oval - shaped (elliptical) orbit. according to kepler’s laws, how does the orbital speed of these planets change as they travel around the sun?
hint 1: remember kepler’s laws—planets move faster when they are closer to the sun and slower when they are farther away.
hint 2: since venus’s orbit is almost a circle, it stays about the same distance from the sun, so its speed doesn’t change much. mars’s orbit is more oval, so its distance from the sun changes more, which means its speed changes more, too.
(1 point)
○ mars changes speed more than venus as it travels around the sun
○ venus changes speed a lot, while mars travels at a constant speed
○ both planets slow down and speed up by exactly the same amounts
○ both planets always travel at exactly the same speed throughout their orbits

Explanation:

1. Analyze Venus: Its orbit is nearly circular, so its distance from the Sun is relatively constant. By Kepler’s laws, speed depends on distance from the Sun (faster when closer, slower when farther). Since Venus’ distance doesn’t change much, its speed change is minimal.
2. Analyze Mars: Its orbit is elliptical (oval - shaped), so its distance from the Sun changes more. As per Kepler’s laws, this means its speed (which depends on distance from the Sun) will change more as it moves closer to or farther from the Sun.
3. Evaluate options:

• Option 1: "Mars changes speed more than Venus as it travels around the Sun" matches the analysis (Venus’ speed change is small, Mars’ is larger).
• Option 2: Says Venus changes speed a lot and Mars has constant speed, which is wrong (Venus’ speed change is small, Mars’ speed changes).
• Option 3: Claims both change speed by the same amount, but Mars’ distance change is more, so speed change should be more for Mars. Wrong.
• Option 4: Says both have constant speed, but Kepler’s laws state speed changes with distance from the Sun. Wrong.

Answer:

A. Mars changes speed more than Venus as it travels around the Sun