Question

Pictured above is a planet in its orbit around a star. Rank the locations according to the speed of the planet at that location greatest first.

• A. 1, 2, 3, 4
• B. 4, 3, 1, 2
• C. 2, 1, 3, 4
• D. 3, 1, 2, 4
• E. At all locations the planet travels at the same speed.

Answer 1

The correct option is B 4, 3, 1, 2

According to kepler's second law of planetary motion, a planet "sweeps equal areas in equal time". This means that a planet must be moving faster when it is closer to the star than when it is further away.

This can also be explained by conservation of angular momentum or by conservation of energy

the order of speed from greatest to least is same as order of distance to the star from least to greatest : 4,3,1,2

so the correct answer is choice "B"