本题目来源于试卷: 2011 美国F=ma物理竞赛 F=ma physics competition，类别为 美国物理杯赛(Physics Bowl)
[单选题]
A particle is launched from the surface .q*tnht zvm3(my, u(/ivuo 5kof a cfmf *k* mvz;1hi54lj6u ww4 huniform, stationary spherical planet at an angle to the vertical. The particle travels in the absence of air resistance and evef5l1i;4zwfvhum * k*hcm6 j4 wntually falls back onto the planet. Spaceman Fred describes the path of the particle as a parabola using the laws of projectile motion. Spacewoman Kate recalls from Keplers laws that every bound orbit
around a point mass is an ellipse (or circle), and that the gravitation due to a uniform sphere is identical to that of a point mass. Which of the following best explains the discrepancy?
A. Because the experiment takes place very close to the surface of the sphere, it is no longer valid to replace the sphere with a point mass.
B. Because the particle strikes the ground, it is not in orbit of the planet and therefore can follow a nonelliptical path.
C. Kate disregarded the fact that motions around a point mass may also be parabolas or hyperbolas.
D. Keplers laws only hold in the limit of large orbits.
E. The path is an ellipse, but is very close to a parabola due to the short length of the flight relative to the distance from the center of the planet.
参考答案: A
本题详细解析:
暂无
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