One or more options correct
A satellite moves in a circular orbit of radius about a planet of mass (speed , period ). By a short rocket burn its speed is suddenly raised to along the direction of motion. Choose the correct statement(s).
- A. The new orbit is an ellipse with farthest distance from the planet's centre.
- B. The speed at the farthest point is .
- C. The new orbital period is about .
- D. The total mechanical energy of the satellite in the new orbit is positive.
Show answer and solution
Answer: A, B, C
With , the new specific energy is . For an ellipse , so . The burn point is the nearest point (velocity is perpendicular to the radius), so the farthest distance is : (A) is true. Angular momentum conservation gives , so : (B) is true. Kepler's third law gives : (C) is true. The energy is negative (, since the escape speed ratio), so the orbit is bound: (D) is false. Kepler's second law is consistent with this: the satellite moves slowest at the farthest point, where the speed is only of the original circular speed, and fastest at the burn point where it began.
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