How many days would be in a year if the distance between the earth and the sun were reduced to half of its present value (assuming circular orbit) ?
Correct answer: D. 129 days
- A. 365 days
- B. 730 days
- C. 329 days
- D. 129 days
Explanation
For circular planetary orbits, Kepler’s third law gives T proportional to r^3/2. Reducing the orbital radius to half gives T' = T(1/2)^3/2 = 365 days × 0.3536 = 129.1 days, approximately 129 days. Students may choose 365 days by assuming the orbital period is unchanged when the radius changes.
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