[填空题]
The Near Earth Asteroid Regicr-yopj.,3d*dv ni x 18 ak3ndezvous (NEAR), afaqku ahtl4w5-v5k h+7 ter traveling 2.1 billion km, is meant to orbit the asteroid Eros at a heighwa 4+ qt75ahvukl5-kht of about 15 km . Eros is roughly 40 $\mathrm{~km} \times 6 \mathrm{~km} \times 6 \mathrm{~km}$ . Assume Eros has a density (mass/volume) of about 2.3 $\times 10^{3} \mathrm{~kg} / \mathrm{m}^{3}$ . (a) What will be the period of NEAR as it orbits Eros? $\approx$ $\times 10^4$sec
(b) If Eros were a sphere with the same mass and density, what would its radius be? $\approx$ $\times 10^3$
(c) What would g be at the surface of this spherical Eros?$\approx$ $\times 10^{-3}$
