[填空题]
1.(1)The Moon orbits the Earth in a cir 49yanjz edclxd/6;h, cular or +0 ypf/- qiaz0*knkxabit. Explain why a centripetal force is needed for the Moon to be in its orbit 00i -+yxq k/knaap*fzaround the Earth.
(2)Identify the origin of this force. v = $\times10^3\,m$
2.(1)Show that the orbital period T of the Moon around the Earth is given by $T=2 \pi \sqrt{\frac{r^3}{GM}}$
where $M$ is the mass of the Earth and $r$ is the orbital radius.
2.Knowing that
Mass of the Earth = $5.98\times10^{24}\,kg$
The orbital radius = $3.84\times10^8\,m$
Calculate the orbital speed of the Moon around the Earth.
3.(1)A total solar eclipse is seen when the Sun, the Moon and the Earth lie on the same line with the Moon in between the Sun and the Earth.
Knowing that
Mass of the Sun = $1.99\times10^{30}\,kg$
Distance between Sun and Moon during eclipse = $1.49\times10^{11}\,m$
Mass of the Moon = $7.36\times10^{22}\,kg$
Determine whether the Sun or the Earth exerts a greater gravitational force on the Moon.
(2)Explain why the Sun doesn't pull the Moon away from the Earth during a total solar eclipse.
