两道天文问题求解!急求高手!5.Understandingtheseasons.Uranusistippedonitsside(itsrotationaxisisparalleltotheecliptic).DescribehowanorthernhemisphereUranianwouldexperiencetheseasonsoverayear.(Hint:drawUranus

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两道天文问题求解!急求高手!
5. Understanding the seasons. Uranus is tipped on its side (its rotation axis is parallel to the ecliptic). Describe how a northern hemisphere Uranian would experience the seasons over a year. (Hint: draw Uranus in its orbit around the sun at both the equinox and solstice positions.)
季节问题.天王星是倾斜的（其转动轴平行于黄道）.描述一下,天王星的北半球在一年中经历了怎样的季节?（提示：画出天王星在绕日轨道上的两分和两至的位置）
7. a. Suppose that instead of dropping a lead ball and a wooden ball from the Leaning Tower of Pisa (where, according to the legend -- and to Newton's Laws, they landed at the same time), Galileo dropped them in deep space, far from any star. Describe what would happen and why. (Assume the lead ball is more massive than the wooden ball, and much less massive than Galileo.)
a假设当初伽利略并没在比萨斜塔上扔下一个铅球跟一个木球,而是在宇宙深处,远离一切恒星的地方进行实验.请描述会发生什么并解释.（假设铅球比木球更重,而比伽利略要轻很多）
b通过绕着地球公转可以逃脱地球引力吗?为什么在宇宙飞船里的宇航员是处于失重状态?请解释
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Answer 1

7:a 铅球和木球会围绕共同的质心做圆周运动,质心靠近铅球.
b 不可以.飞船里的宇航员所受到的引力与绕地球飞行的离心力平衡了,此时宇航员受到的合力为零,所以感到失重